COLUMBIA  LIBRARIES  OFFSITE 

HEALTH  SCIENCES  STANDARD 


HX64070263 
R  K53  .  F73  1916      Mouth  hygiene :  a  co 


!':!'  i 


•,.;i: 


■J.  il:'  'I] 


i'''r] 


Xm 


aniiM«Mra 


liii. 


!:nil 


'I   ■'' r 


II    l! 


m 


■j 


f^irSS  F75 

Columbia  ^nibcri^itp 
intljcCitPof  J^etjj^orfe 

College  of  ^Jjpgicians  anb  burgeons 


Reference  Itifararp 


DR.  WILLIAM  J.  OILS  J"^' 

fo  enrich  the  [ihra.ry  resources 

available  to  holders 

of  the 

GlES  FELLOWSHIP 

in  Biolosica.1  Chemistry 


Digitized  by  the  Internet  Archive 

in  2010  with  funding  from 

Open  Knowledge  Commons 


http://www.archive.org/details/mouthhygienecourOOfone 


CONTBIBUTOES 

ANDERSON,  WILLIAM  G.,  M.D.,  Dr.P.H. 

CHITTENDEN,  RUSSELL  H.,  Ph.D.,  LL.D.,  Sc.D. 

CRAMPTON,  C.  WARD,  M.D. 

FISHER,  IRVING,  Professor 

FONES,  ALFRED  C.,  D.D.S. 

HUTCHINSON,  R.  G.,  Jr.,  D.D.S. 

HYATT,  THADDEUS  P.,  D.D.S. 

KEYES,  FREDERICK  A.,  D.M.D. 

KIRK,  EDWARD  C,  Sc.D.,  D.D.S.,  LL.D. 

MacKEE,  GEORGE  M.,  M.D. 

MINER,  LeROY  M.  S.,  M.D.,  D.M.D. 

O'NEILL,  CORDELIA  L. 

OSBURN,  RAYMOND  C,  Ph.D. 

OTTOLENGUI,  RODRIGUES,  M.D.S.,  D.D.S.,  LL.D. 

PRINCE,  ALEXANDER  M.,  M.D. 

RETTGER.  L.  F.,  Ph.D. 

RHEIN,  M.  L.,  M.D..  D.D.S.,  D.R.C.,  U.S.N. 

STRANG,  ROBERT  H.  W.,  M.D.,  D.D.S. 

TURNER,  CHARLES  R.,  M.D.,  D.D.S. 


MOUTH  HYGIENE 

A  COURSE  OF  INSTRUCTION  FOR  DENTAL 
HYGIENISTS 


A  TEXT-BOOK   CONTAINING   THE   FUNDAMENTALS   FOR 
PKOPHYLACTIC  OPERATORS 


COMPILED  BY 

ALFRED  C.  FONES,  D.D.S. 

BRIDGEPORT,   CONNECTICUT 

EDITED  BY 

EDWARD  C.  KIRK,  Sc.D.,  D.D.S.,  LL.D. 

ROBERT  H.  W.  STRANG,  M.D.,  D.D.S. 

ALFRED  C.  FONES,  D.D.S. 


TKIlitb  278  llllustrationg  anJ)  7  IPlatea 


LEA   &   FEBIGER 

PHILADELPHIA    AND   NEW   YORK 
1916 


Entered  according  to  the  Act  of  Congress,  in  the  j^ear  1916,  by 

LEA   &   FEBIGER, 
In  the  Office  of  the  Librarian  of  Congress.    All  rights  reserved. 


PEEFACE. 


Dentistry  is  in  a  position  today  where  the  problem  of  mouth  hygiene 
must  be  solved  in  a  practical  manner.  The  medical  profession  now 
realizes  that  unsanitary  mouths  with  diseased  teeth  are  a  very  potent 
factor  for  ill  health  and  systemic  infection. 

Although  many  of  the  leading  investigators  and  writers  of  the  dental 
profession  have  repeatedly  called  attention  to  the  rnouth  as  a  cause 
for  systemic  disease,  the  cry  has  not  been  heard  by  the  mother  profes- 
sion until  a  comparatively  recent  period.  Now  that  we  know  that  this 
gateway  to  the  body  must  be  kept  clean,  the  teeth  sound  and  the  gum 
tissue  maintained  in  a  healthy  condition,  the  question  arises  how  such 
an  enormous  work  as  that  which  is  before  our  profession  can  be  suc- 
cessfully accomplished.     Surely  the  dentists  alone  cannot  cope  with  it. 

Judging  from  the  condition  of  the  mouths  of  the  children  in  om* 
public  schools,  fully  90  per  cent,  of  the  population  of  this  country 
has  decayed  teeth.  If  all  the  dentists  in  the  United  States  devoted 
all  of  their  time  to  reparative  work  alone,  they  could  not  take  care  of 
one-eighth  of  the  people.  But  operative  dentistry  is  expensive.  It  is 
beyond  the  means  of  the  great  working  class  who  need  sound  teeth 
and  good  health.  There  must  be  some  cheaper  and  better  solution 
than  merely  to  follow  the  endless  chain  of  repair.  We  must  get  at 
the  source  of  this  universal  disease  and  try  to  check  it  by  educational 
and  preventive  means. 

The  source  is  the  children  in  our  public  schools.  We  know  that 
with  extreme  cleanliness,  the  elimination  of  improper  foods  and  with 
surface  treatments  of  the  teeth  at  regular  intervals,  fully  90  per  cent, 
of  dental  decay  can  be  eliminated.  If  this  knowledge  and  service 
is  to  be  given  to  the  children  as  well  as  to  those  adults  who 
are  patients  in  private  practice,  who  is  to  give  it?  Apparently  the 
only  solution  is  the  woman  who  is  educated  and  trained  as  a  dental 
hygienist. 

This  is  woman's  work  and  there  is  an  immense  field  open  for  thou- 
sands of  women  in  dental  offices  and  public  institutions.  Such  a  course 
of  education  and  instruction  should  also  be  annexed  to  the  training 
of  the  medical  nurse,  as  her  services  for  mouth  hygiene  in  the  hospitals 
and  sanitariums  would  soon  prove  to  be  invaluable.  These  questions 
have  repeatedly  been  asked,  "  Where  are  we  going  to  secure  such  women, 
educated  and  trained  as  dental  hygienists  ?  Where  are  they  to  secin-e 
such  an  education?    What  should  constitute  such  a  course  for  lectures 


vi  PREFACE 

and  practical  training?    Are  there  text-books  that  they  may  study  to 
comprehend  and  perfect  themselves  in  this  preventive  work?" 

The  main  object  of  this  publication  is  to  present  a  definite  answer 
to  these  questions  and  introduce  an  educational  course  for  dental 
hygienists  that  will  prove  to  be  something  definite  and  tangible  at 
tiie  start. 

In  the  fall  of  1913  the  gentlemen  whose  names  appear  as  contrib- 
utors to  this  work  were  approached  and  asked  if  they  would  aid  in 
such  a  cause,  if  they  would  come  to  Bridgeport  and  deliver  their 
lectures  to  a  class  of  thirty -two  women,  the  lectures  to  be  taken 
in  shorthand,  sent  to  them  for  correction  and  condensation  so  that 
the  pith  of  the  subject  might  be  published  in  a  text-book  for  the 
education  of  women  assistants  in  prophylaxis. 

Without  exception  these  gentlemen  agreed  to  come.  The  lectures 
were  held  in  the  evenings  on  Mondays,  Wednesdays  and  Fridays, 
and  with  the  exception  of  a  vacation  at  Christmas  time,  ran  from 
November  17  until  March  30. 

The  class  assembled  at  7.30  p.m.  and  a  review  of  previous  lectures 
was  taken  up  by  one  of  the  quiz  masters.  At  8  p.m.  the  lecturer 
of  the  evening  commenced,  and  lectured  until  9.30  p.m.  or  there- 
abouts. Eleven  ^\Titten  examinations  were  held  and  out  of  a  class 
of  thirty-two,  all  but  six  passed  with  an  average  above  70  per  cent., 
and  nine  passed  above  90  per  cent. 

It  is  our  earnest  desire  that  educational  institutions,  such  as  dental 
colleges,  will  take  up  this  work  and  establish  a  course  of  education 
and  training  for  women  as  dental  hygienists.  We  believe  that  the  title, 
dental  nurse,  is  a  misnomer,  as  these  M^omen  are  not  to  perform  any 
service  that  resembles  the  work  of  the  medical  nurse.  They  are  pro- 
phylactic operators  and,  although  they  have  a  knowledge  of  dental  dis- 
eases, their  service  is  limited  by  law  to  prophylactic  work.  When  the 
value  of  a  service  such  as  theirs  is  fully  appreciated  by  the  dental  and 
medical  professions,  there  will  be  a  great  demand  for  these  practical 
workers  for  mouth  hygiene,  not  only  in  i)rivate  offices  but  in  the  public 
schools.  It  is  our  hope  that  this  educational  course  will  help  to  sjK'cd 
the  day. 

A  full  description  of  the  methoils  emi)loyed  for  the  practical  train- 
ing will  be  found  in    the  ii,])i)(n(lix. 

Aside  from  our  obligation  to  the  lecturers,  quiz  masters,  a  loyal 
office  force  and  a  numl^er  of  kind  friends  who  are  influential  in  the  den- 
tal profession  and  whose  aid  proved  so  valuable,  we  are  also  grateful 
to  the  S.  S.  White  Dental  ^Manufacturing  Company  for  their  display 
of  generosity  in  loaning  us  sixteen  new  Diamond  chairs  for  our  course 
in  ])ractical  training. 

A.  C.  F. 

BitiDGEPouT,  Conn.,  1010. 


LIST  OF  CONTRIBUTORS. 


WILLIAM   G.  ANDERSON,  Dr.P.H.,  M.D., 

Professor  and  Director  of  Yale  Universitj'  Gymnasium. 

RUSSELL  H.  CHITTENDEN,  Ph.D.,  LL.D.,  Sc.D., 

Director  of  Sheffield  Scientific  School  of  Yale  University. 

C.  WARD  CRAMPTON,  M.D., 

Hygienist  and  Director  of  Physical  Training,  Public  School  System,  New  York 
City. 

PROFESSOR  IRVING  FISHER, 

Chairman    of  Committee  of   One  Hundred  on  National  Hygiene,  of   Yale 
L'niversitj',  New  Haven,  Conn. 

ALFRED  C.  FONES,  D.D.S., 
Bridgeport,  Conn. 

R.  G.  HUTCHINSON,  Jr.,  D.D.S., 

Specialist  in  Treatment  of  Pyorrhea  Alveolaris,  New  York  City. 

THADDEUS  P.  HYATT,  D.D.S., 
New  York  City. 

FREDERICK  A.  IiI]YES,  D.M.D., 

New  York  City. 

EDWARD   C.   KIRK,  Sc.D.,  D.D.S.,  LL.D., 

Dean  of  Dental  Department  of  the  University  of  Pennsylvania,  Philadelphia. 

GEORGE   M.  :MacKEE,  M.D., 

Instructor  in  Dermatology  in  the  College  of  Physicians  and  Surgeons,  New 
York  City.     Editor  of  Journal  of  Cutaneous  Diseases. 

LEROY   M.  S.  MINER,  M.D.,  D.M.D., 

Assistant  Professor  in  Surgery  in  the  Harvard  Dental  School,  Boston,  Mass. 

MISS   CORDELIA  L.  O'NEILL, 

Principal  of  Clarion  School,  Cleveland,  Ohio. 

RAYMOND  C.  OSBURN,  Ph.D., 

Professor  of  Biology,  Connecticut  College  for  Women,  New  London,  Conn. 

RODRIGUES  OTTOLENGUI,  M.D.S.,  D.D.S.,  LL.D., 
Editor  of  Items  of  Interest,  New  York  City. 


viii  LIST  OF  CONTRIBUTORS 

ALEXANDER  M.  PRINCE,  M.D., 

Instructor  in  Medicine  and  Physiology,  Medical  Department  of  Yale  Uni- 
versity, New  Haven,  Conn. 

L.  F.  RETTGER,  Ph.D., 

Assistant  Professor  of  Bacteriologj'-  in  the  Sheffield  Scientific  School  of  Yale 
University,  New  Haven,  Conn. 

M.  L.  RHEIN,  M.D.,  D.D.S., 

Lecturer  on  Dental  Pathology  in  the  Dental  Department  of  the  University 
of  Pennsylvania  (Philadelphia),  New  York  City. 

ROBERT  H.  W.  STRANG,  M.D.,  D.D.S., 

Specialist  in  Orthodoatia,  Bridgeport,  Conn. 

CHARLES   R.  TURNER,  M.D.,  D.D.S., 

Professor  of  Prosthetic  Dentistry  and  Metallurgy  in  the  Dental  Department 
of  the  University  of  Pennsylvania,  Philadelphia. 


CONTENTS. 


CHAPTER  I. 

ANATOMY 17 

By  Raymond  C.  Osburx,  Ph.D. 

CHAPTER  II. 

SPECIAL  ANATOMY ^ 57 

By  Robert  H.  W.  Strang,  M.D.,  D.D.S. 

CHAPTER  III. 

PHYSIOLOGY 104 

By  Alexander  M.  Prince,  M.D. 

CHAPTER  IV. 

BACTERIOLOGY  AND  STERILIZATION 130 

By  L.  F.  Rettger,  Ph.D. 

CHAPTER  V. 

INFLAMMATION 158 

By  LeRoy  M.  S.  Miner,  M.D.,  D.M.D. 

CHAPTER  VL 

DEPOSITS  AND  ACCRETIONS  UPON  THE  TEETH 170 

By  Edward  C.  Kirk,"  Sc.D.,  D.D.S.,  LL.D. 

CHAPTER  VII. 

DENTAL  CARIES • 187 

By  Edward  C.  Kirk,  Sc.D.,  D.D.S.,  LL.D. 

CHAPTER  VIII. 

THE  TEETH  AS  A  MASTICATING  MACHINE 205 

By  Charles  R.  Turner,  M.D.,  D.D.S. 


X  CONTENTS^ 

CHAPTER  IX. 

MALOCCLUSION  OF  THE  TEETH 237 

By  Rodrigues  Ottolengui,  M.D.S.,  D.D.S.,  LL.D. 

CHAPTER  X. 

PYORRHEA  ALVEOLARIS 261 

By  R.  G.  Hutchinson,  Jr.,  D.D.S. 

CHAPTER  XI. 

ODONTALGIA  AND  ALVEOLAR  ABSCESS 266 

By  M.  L.  Rhein,  M.D.,  D.D.S.,  D.R.C.,  U.S.N. 

CHAPTER  XII. 
DENTAL  PROPHYLAXIS 288 

By  Alfred  C.  Fones,  D.D.S. 

CHAPTER  XIII. 

CHEMISTRY  OF  FOOD  AND  NUTRITION 367 

By  Russell  H.  Chittenden,  Ph.D.,  LL.D.,  Sc.D. 

CHAPTER  XIV. 

DERMATOLOGY 401 

By  George  M.  MacKee,  M.D. 

CHAPTER  XV. 

FACTORS  IN  PERSONAL  HYGIENE 429 

By  C.  Ward  Crampton,  M.D. 

CHAPTER  XVI. 

FRESH  AIR  AND  CORRECT  POSTURE  IN  THEIR  RELATION  TO 

HYGIENE 440 

By  Professor  Irving  Fisher. 

CHAPTER  XVII. 

LENGTHENING  THE  LIFE  OF  THE  RESISTIVE  FORCES  OF  THE 

BODY 449 

By  Willia.m  G.  Anderson,  M.D.,  Dr.P.H. 


CONTENTS  xi 

CHAPTER  XVIII. 

THE  TEACHING  OF  MOUTH  HYGIENE  TO  SCHOOL  CHILDREN     459 
By  Thaddeus  P.  Hyatt,  D.D.S. 

CHAPTER  XIX. 

INSTITUTIONAL  DENTISTRY 463 

By  a.  C.  Fones,  D.D.S., 
Frederick  A.  Keyes,  D.M.D., 

AND 

Cordelia   L.  O'Neill. 

APPENDIX 505 

INDEX 521 


MOUTH  HYGIENE. 


CHAPTER  I. 
ANATOMY. 

By  RAYMOND  C.  OSBURN,  Ph.D. 

ANALYSIS    OF    THE    ORGANISM. 

.[naiomy  is  the  science  which  treats  of  the  structure  of  organ i.wis 
or  hving  beings.  The  different  parts  of  an  organism,  called  organs, 
are  each  fitted  for  the  performance  of  one  or  more  kinds  of  work.  Any 
particular  kind  of  work,  or  special  part  of  the  vital  process,  is  known 
as  a  function. 

Organs  are  said  to  be  specialized  or  differentiated  for  the  perform- 
ance of  their  various  functions.  Structural  differentiation  enables  an 
organ  to  perform  its  particular  duty  more  readily,  hence  we  say  that 
it  is  adapted  to  its  function.  Thus  in  the  human  body  the  liver, 
kidney,  ear  and  eye  have  certain  definite  kinds  of  work  to  do,  and  so 
on  throughout  the  long  list  of  organs.  This  setting  aside  of  special 
parts  for  particular  uses,  termed  biological  divisio7i  of  labor,  has  come 
about  gradually  during  the  course  of  evolution. 

Anatomy  is  not  only  interesting  in  itself,  but  it  is  necessary  to  the 
study  of  physiology  and  the  phenomena  of  life  generally.  One  would 
not  expect  to  understand  how  a  watch  keeps  time  until  he  knew  the 
parts  concerned,  as  the  main  spring,  the  hair  spring,  the  balance 
wheel,  etc.,  and  the  relationship  which  these  parts  bear  to  each  other. 
So  one  need  not  expect  to  understand  how  the  human  body  does  its 
work  without  knowing  the  parts  that  enter  into  its  formation  and  how 
these  are  related  in  the  body  complex.  Furthermore,  in  this  course 
of  study,  in  preparation  for  work  upon  an  important  part  of  the  body, 
anatomy  has  an  intensely  practical  interest. 

SYSTEM    OF    ORGANS. 

One  of  the  first  things  we  observe  when  we  examine  the  organs  of 

any  higher  animal  is  that  they  are  often  related  to  each  other  in  a 

definite  way  for  the  purpose  of  carrying  on  some  work  too  complicated 

to  be  handled  satisfactorily  by  a  single  organ.     Such  arrangements  of 

2 


18 


ANATOMY 


organs  are  called  systems.  In  the  alimentary  system,  for  example,  the 
mouth,  the  pharynx,  gullet,  stomach,  small  intestine,  and  large  intes- 
tine are  all  distinct  organs  having  different  functions  to  perform,  but 
all  operate  in  series  to  handle,  digest  and  absorb  the  food.  Similarly, 
in  the  circulatory  system,  the  heart,  arteries,  capillaries,  veins,  and 
lymphatics  all  have  different  things  to  do,  but  all  work  together 
toward  the  one  end  of  circulating  the  fluids  of  the  body. 
Classification  of  Systems:  -^ 

Individual.       ^-r/^^^.^^-i^'*^' 


Nutritional 


Relational 


Alimentary 

Respiratory 

Circulatory 

Excretory 

Motor 

Supporting 

Nervous 

Reproductive 


Racial. 


The  nutritional  systems  are  those  which  supply  food  and  oxygen, 
circulate  or  distribute  them,  and  collect  wastes  and  eliminate  them 
from  the  body;  in  other  words  they  work  in  harmony  toward  the 
nutrition  of  the  body.  The  relational  systems  relate  or  coordinate  the 
various  parts  of  the  body  with  each  other  and  the  organism  as  a  whole 
with  the  outside  world.  All  of  these  are  concerned  primarily  with  the 
welfare  of  the  individual,  so  may  all  be  classed  together  as  the  indi- 
vidual systems.  On  the  other  hand,  the  rejiroductive  system  has  to  do 
with  the  propagation  of  the  species  and  is  therefore  of  racial  importance. 
The  various  systems  and  their  organs  will  be  considered  separately 
later. 

STRUCTURE    OF    ORGANS;    HISTOLOGY. 

Anatomy  does  not  stop  with  the  analysis  of  the  organism  into  organs 
but  considers  also  the  structure  of  the  organs  themselves.  Here 
again  we  find  both  structural  differentiation  and  division  of  labor, 
for  these  always  go  hand-in-hand,  and  each  part  of  every  organ  is 
developed  in  its  particular  position  and  is  structurally  suited  to  its 
special  duty. 

The  study  of  the  organs  and  systems  is  commonly  called  r//o.s-.s- 
anatomy.  The  finer  parts  of  which  the  organs  are  made  up  must  be 
studied  with  the  aid  of  a  microscope,  and  this  field  of  work  is  therefore 
known   as  mlcrosropir  auatonii/  or  histdldfu/. 

Tissues. — The  organs  of  the  human  body,  in  s])itc  of  their  manifold 
duties,  are  made  up  of  a  very  limited  number  of  common  building 
stuffs.     These  we  call  tissues. 

An  organ  consists  of  several  kinds  of  tissues  intimately  l)ound 
together.  The  hanfl,  for  example,  though  one  organ,  consists  of  the 
.skin,  muscles,  bones,  cartilages,  nerves,  blood,  fat  and  fibrous  connec- 
tive tissues.    The  tongue  consists  of  epithelial  tissue  on  the  outside, 


STRUCTURE  OF  ORGANS— HISTOLOGY  19 

while  within  are  several  sets  of  muscles,  the  nerves,  blood  and  con- 
nective tissues.  And  so  in  any  organ  various  sorts  of  tissues  are 
blended,  according  to  the  work  for  which  it  has  been  specialized. 

Furthermore,  the  same  tissue  may  be  found  in  difi'erent  organs. 
Thus,  no  organ  is  without  nervous  tissue  for  sensation  and  for  coordi- 
nating and  regulating  the  parts;  muscular  tissue  is  distributed  in  all 
the  organs  of  the  body,  and  connective  tissues  occur  everywhere  to 
bind  the  other  parts  together. 

Classification  of  Tissues: 
I.  Epithelial. 
11.  Supporting. 

III.  Circulatory. 

IV.  Glandular. 
V.  Motor. 

VI.  Nervous. 
VII.  Reproductive. 
These  may  be  taken  up  in  order  for  further  discussion. 

I.  Epithelial  tissues  are  those  which  cover  surfaces  on  or  within 
the  body,  such  as  the  epidermis  forming  the  outer  skin;  mucous 
membranes  which  line  the  alimentary  tract,  the  lungs,  the  air  passages, 
and  the  nasal  cavities;  and  serous  membranes  (sometimes  called  endo- 
thelial) which  line  the  closed  cavities  of  the  body,  as  the  peritoneum 
of  the  general  abdominal  cavity,  the  pleurae  lining  the  space  about 
the  lungs,  the  lining  of  the  heart  and  bloodvessels,  etc. 

II.  Supjjorting  tissues  are  of  many  kinds  and  serve  variously  to 
give  form  and  rigidity,  to  connect  organs  and  to  bind  other  tissues 
together  that  they  may  be  held  in  their  proper  place.  Bone  forms 
the  general  skeletal  framework  and  is  the  firmest  of  all  the  tissues. 
Cartilage,  or  gristle,  serves  to  support  parts  that  need  more  or  less 
flexibility,  such  as  the  external  ear  and  the  tip  of  the  nose,  as  well  as 
to  connect  the  ribs  with  the  breast-bone  or  sternum,  and  it  is  usually 
found  also  between  the  bones  at  the  joints  w^here  it  prevents  shock. 
Tendons  are  found  chiefly  as  the  cords  which  connect  the  muscles 
with  the  bones  to  which  they  are  attached.  Ligamenis  bind  the  bones 
together  at  the  joints  and  hold  certain  other  organs  in  place.  White 
fibrous  tissue,  in  the  form  of  minute  crinkly  fibers,  is  distributed  every- 
where among  the  other  tissues  (except  in  epithelia  which  it  underlies) 
and  forms  the  common  binding  substance  which  holds  other  tissues 
in  place.  Yellow  elastic  tissue  is  made  up  of  delicate,  straight,  branched 
fibers  that  are  like  so  many  little  rubber  bands.  It  serves  to  pull 
back  into  place  any  tissue  that  has  been  temporarily  distorted. 

III.  The  circulatory  tissues  consist  of  the  blood  and  lymph  cells, 
together  with  the  fluids  in  w^hich  they  are  carried. 

IV.  Glandular  tissues  are  those  which  have  the  power  of  picking  up 
minute  quantities  of  substances  from  the  blood  and  concentrating 
them,  or  of  elaborating  substances  into  the  forms  in  which  they  are 
again  given  out  in  secretion  and  excretion. 


20  ANATOMY 

V.  Motor  tissves  consist  of  muscle  cells  of  three  different  kinds; 
the  iinstriped  or  involimtary,  such  as  those  in  the  wall  of  the  intestine; 
the  cardiac,  which  form  the  muscular  walls  of  the  heart;  and  the  striped 
or  so-called  voluntary  muscle  cells,  which  form  the  great  mass  of  the 
body  wall  and  limb  muscles. 

VI.  Nervous  tissues  are  made  up  of  the  nerve  cells  with  their  fibers 
and  the  end-organs  of  the  special  senses. 

The  brain  and  spinal  cord  are  merely  aggregations  of  nerve  cells  and 
fibers  bound  together  by  connective  tissue. 

VII.  Reproductive  tissues  are  differentiated  in  the  two  sexes.  In 
the  female  they  are  the  ovarian  tissues  which  give  rise  to  the  ova  or 
egg  cells  and  in  the  male  they  are  the  spermatic  tissues  which  give  rise 
to  the  male  cells  or  spermatozoa. 

Tissues  can  perform  only  the  particular  kinds  of  work  for  which 
they  are  adapted,  and  each  cell  of  any  tissue  performs  the  same  func- 
tion as  all  the  other  cells  of  that  tissue.  This  is  true  no  matter  in 
what  part  of  the  body  they  may  be  located.  Thus,  muscle  cells 
contract,  though  found  in  the  hand,  heart,  eye,  or  stomach;  nervous 
tissues  are  capable  of  stimulation  and  conduct  impulses  wherever 
they  may  be,  etc. 

A  tissue  may  be  best  defined  as  consisting  of  similar  cells  all  of 
which  do  the  same  kind  of  work. 

•The  Cell. — Cells  are  the  fundamental  structures  of  the  organism. 
They  are  the  physical  units,  out  of  w^hich  all  the  tissues,  therefore  all 
the  organs,  and  the  organism  itself,  are  constructed.  Cells  differ 
greatly  among  themselves  in  size,  form,  internal  structure  and  in 
function. 

They  are  classified  according  to  the  tissues  in  which  they  occur. 
Thus  in  epithelial  tissue  we  find  epithelial  cells,  bony  tissue  contains 
bone  cells,  glandular  tissue  contains  gland  cells,  and  so  on  through  the 
list. 

Structure  of  the  Cell  (Fig.  1). — ^The  all-important  substance  in  the 
cell  is  that  to  which  we  apply  the  name  protoplasm .  It  was  originally 
applied  to  the  living  matter  of  minute  one-celled  organisms,  and  meant, 
therefore,  the  simplest  living  substance.  But  later  chemical  and 
microscopic  studies  have  shown  that  this  substance  has  the  same 
general  properties  as  the  living  matter  of  all  cells  of  all  organisms,  both 
plant  and  animal. 

Protoplasm,  in  all  jjrobability,  is  a  mixture  of  substances,  chemically 
speaking,  but  the  one  thing  that  distinguishes  it  at  once  from  any 
other  material  is  the  fact  that  it  is  alive.  All  the  functions  of  the  body, 
no  matter  what  they  are,  originate  directly  in  the  protoplasm.  It 
should  })e  evident  that  it  varies  somewhat  in  the  different  cells,  since 
these  are  capable  of  doing  different  kinds  of  work.  However,  in  all 
cases  the  work  is  performed  by  lixing  matter  and  there  is  no  living 
substance  but  protoplasm. 

Under  the  microscoijc  the  protoplasm  appears  as  a  rather  thickish, 


STRUCTURE  OF  ORGANS—HISTOLOGY  21 

nearly  clear  fluid,  which  is  usually  slightly  granular,  but  may  appear 
quite  homogeneous  when  alive. 

The  protoplasm  in  a  cell  is  divided  into  two  portions.  The  larger 
part  forms  the  general  cell  fluid,  known  as  the  cytoplasm.  Within 
this,  usually  near  the  center  of  the  cell,  is  the  nucleus.  This  consists 
of  a  denser  fluid  which  does  not  mix  with  the  cytoi)lasm.  Occasionally 
more  than  one  nucleus  is  present.  Both  the  cytoi)lasm  and  the  nucleus 
are  alive,  and  both  take  part  in  the  activities  of  the  cell. 

Usually  there  is  also  j)resent  a  limiting  membrane  about  the  proto- 
plasm, forming  the  cell  wall  or  cell  membrane.  This  structure  is  not 
li\ing  and  therefore  is  not  protoplasm,  but  it  is  formed  by  the  proto- 
plasm as  a  secretion. 


Fig.  1. — Diagram  of  a  cell.     (F.  H.  Gerrish.) 

Intercellular  Substances. — In  addition  to  the  living  matter  of  the 
body,  forming  the  cells,  there  is  present  a  great  deal  of  very  essential 
non-living  matter  which  is  known  as  intercellular  substance ,  because  it 
is  found  between  the  cells.  This  substance  varies  in  extent  and 
character  according  to  the  tissue  of  which  it  forms  a  part.  One  would 
not  expect  to  find  the  same  kind  of  intercellular  substance  between 
the  cells  of  the  brain  as  in  muscle,  nor  the  same  in  bone  as  in  cartilage, 
and  so  on.  It  is  secreted  by  the  cells  which  are  embedded  in  it.  It  may 
be  very  scanty,  as  in  the  epidermis,  or  abundant,  as  in  the  connective 
tissues.  If  we  examine  cartilage  (Fig.  2)  we  find  that  the  cells  are 
imbedded  in  a  mass  of  translucent,  rubbery  material,  which  is  present 
in  such  quantity  that  the  cells  are  often  widely  separated.  It  is 
this  substance  which  gives  cartilage  or  gristle  its  peculiar  toughness 
and  elasticity.  Tendons  are  composed  of  parallel  fibers  between  which 
the  cells  are  imbedded.  These  tough,  inelastic  fibers,  which  form  the 
larger  part  of  the  tendon,  give  it  its  special  character  as  the  connecting 
structure  between  muscle  and  bone.  In  the  bones  and  teeth  the 
intercellular  substance  is  impregnated  with  lime  salts  to  give  great 
hardness  and  rigidity.  The  supporting  and  connecting  tissues  in 
general  contain  great  quantities  of  intercellular  matter. 

To  summarize:  cells,  consisting  of  protoplasm,  together  with  the 
intercellular  substance,  make  up  the  tissues.     Tissues  are  intimately 


22  ANATOMY 

blended  to  form  organs.  Organs  may  function  alone  or  in  connection 
with  others  in  systems.  The  whole  complex  of  organs  and  systems 
makes  up  the  organism  or  living  body. 


Fig.  2. — Articular  hyaline  cartilage  from  the  femur  of  an  ox:  s,  intercellular 
substance;  p,  protoplasmic  cell;  n,  nucleus.     (Ranvier.) 

THE   NUTRITIVE    SYSTEMS. 

Organs  have  alreadj^  been  defined  as  parts  of  the  body  which  per- 
form different  kinds  of  work,  and  systems  as  series  or  groups  of  organs 
which  work  together  toward  some  greater  end  than  can  be  attained  by 
a  single  organ.  It  is  axiomatic,  of  course,  that  no  organ  or  system 
is  entirely  independent  of  the  others.  This  conception  is  at  least 
as  old  as  J^sop's  fable  of  "The  Belly  and  the  INIembers."  However, 
for  the  purpose  of  analysis  they  may  be  considered  separately. 

The  alimentary,  respiratory,  circulatory,  and  excretory  systems 
have  already  been  mentioned  as  forming  the  nutritional  group.  All 
of  these  systems  are  concerned  with  supplying  nutritive  substances 
to  the  body  or  its  various  parts,  or  with  the  removal  of  wastes  that 
have  accumulated  in  the  process  of  nutrition  and  work. 

The  real  chahi  of  events  in  nutrition  is  as  follows: 

1.  Alimentation,  the  mechanical  handling  of  the  food. 

2.  Digestion,  the  chemical  breaking  up  of  the  food. 

3.  Absorption  of  food  and  water  by  the  alimentary  system. 

4.  Absorption  cjf  oxygen  by  the  resjjiratory  system. 

5.  Circulation,  to  jjass  these  substances  to  the  cells  where  they  are 
used. 


THE  ALIMENTARY  SYSTEM 


23 


6.  Metabolism. 

(a)  Anabolism,  the  l)iiil<lin<^  up  or  eonstrueting  phase,  by  which 
foods  are  comerted  into  protoplasm  or  into  something 
out  of  which  the  prot()})lasni  can  obtain  energy. 

(h)  Katabolism,  the  breaking-down  process  by  which  energy  is 
released  and  wastes  are  formed. 

7.  Circulation  again  in  order  to  collect  the  wastes  formed  in 
the  cells  and  deli\'er  them  to  the  places  where  they  can  be  elimi- 
nated. 

8.  Excretion  in  its  various  j)hases,  in\'olving  especially  the  kidneys, 
lungs  and  skin. 

All  of  the  above  processes,  except  those  of  metabolism  which  take 
place  in  all  the  cells  of  the  body,  are  carried  on  by  the  four  systems 
mentioned  above. 


MOUTH 


SALIVARY 

GLANDS 


SMALL 
INTESTINE 


ANUS 
Fig.  3. — Diagram  of  the  alimentary  tube  and  its  appendages.     (Testut.) 


THE    ALIMENTARY    SYSTEM  (Fig.  3). 

In  this  system  are  included  all  those  organs  which  make  up  the  food 
tube  through  the  body,  beginning  with  the  mouth  and  ending  with 


24  ANATOMY 

the  anus,  together  with  a  number  of  appended  organs.     We  may  list 
these  as  follows: 

1.  Mouth. 

2.  Pharynx. 

3.  Esophagus  or  gullet. 

4.  Stomach. 

5.  Small  intestine. 

6.  Large  intestine  or  colon. 

7.  Anus. 

These  parts  make  up  the  alimentary  tube,  but,  to  complete  the 
system,  there  must  be  added  the  following  glands: 

8.  Salivary  glands. 

9.  Pancreas. 
10.  Liver. 

The  alimentary  tube  is  much  longer  than  the  body  through  which  it 
runs,  being  in  all  about  twenty-eight  feet  in  length.  Most  of  this 
length  is  found  in  the  small  and  large  intestines  which  are  folded  back 
and  forth  in  the  abdominal  cavity  to  accommodate  them  to  the  space. 

Organs  of  the  Alimentary  System. — 1 .  The  Mouth. — The  mouth  will 
be  considered  in  tletail  in  the  chapter  on  Special  Anatomy. 

2.  The  Pharynx. — ^The  pharynx  is  a  musculomembranous  passage, 
somewhat  conical  in  form,  about  five  inches  in  length,  and  suspended 
from  the  base  of  the  skull  just  in  front  of  the  spinal  column.  Above, 
it  communicates  with  the  nose  and  mouth  through  their  posterior 
openings.  At  its  lower  end  and  in  front  is  the  opening  into  the  larynx, 
closed  during  the  act  of  swallowing  by  the  epiglottis.  The  pharynx 
is  continued  below  into  the  esophagus. 

On  the  upper  portion  of  the  lateral  walls  of  the  pharynx  are  seen 
the  openings  into  the  Eustachian  tubes.  Between  these,  on  the  pos- 
terior wall,  is  a  mass  of  lymphoid  tissue  known  as  the  pharyngeal 
tonsil.  When  this  becomes  hypertrophied,  as  it  often  does  in  children, 
it  gives  rise  to  the  condition  known  as  adenoids. 

3.  Esophagus. — This  is  a  nearly  straight  tube,  about  nine  inches 
in  length,  which  extends  from  the  pharynx  to  the  stomach,  behind  the 
windpipe  or  trachea,  piercing  the  diaphragm.  As  in  other  parts  of 
the  intestinal  tract,  its  collapsible  wall  closes  the  passage  except  when 
food  or  water  is  passing  through  it.  Its  walls  are  provided  with 
muscles  to  further  the  process  of  swallowing. 

4.  Stomach  (Fig.  4). — This  is  the  most  expanded  portion  of  the 
tube  and  serves  as  a  crop  or  receptacle  for  food,  in  addition  to  which  it 
assists  in  the  digestion  of  the  protein  foods.  It  lies  obliquely  across 
the  left  side  of  the  body  just  below  the  diaphragm.  Its  larger  end, 
known  as  the  fundvfi,  is  connected  with  the  esophagus,  and  a  sphincter 
or  circular  muscle,  the  cardiac  valve,  guards  the  aperture  against  the 
return  of  food  into  the  esophagus.  The  smaller  end,  toward  the  right, 
is  known  as  the  pylorus  and  this  communicates  with  the  duodenum 
through  an  opening  guarded  by  another  sphincter  called  the  yyloric 


THE  ALIMENTARY  SYSTEM 


25 


valve.  The  average  capacity  of  the  stomach  is  about  a  quart.  It  is 
lined  with  mucous  membrane  in  which  many  small  tubular  glands,  the 
gastric  glands,  are  imbedded.  It  has  three  muscular  coats,  one  more 
than  the  intestine,  namely  the  longitudinal,  the  circular  and  the  oblique. 


Fig.  4. — The  stomach  and  intestines,  front  view,  the  groat  omentum  having  been 
removed,  and  the  Hver  turned  up  and  to  the  right.  The  dotted  Une  shows  the  normal 
position  of  the  anterior  border  of  the  liver.  The  dart  points  to  the  foramen  of  Winslow. 
(Testut.) 

and  is  covered  on  the  outside  by  the  smooth  serous  layer  of  the  ^^eri- 
toneum  which  prevents  friction. 

5.  Small  Intestine  (Fig.  4). — This  tube  is  about  twenty  feet  long  and 
varies  in  diameter  from  nearly  two  inches  at  its  upper  end  to  about  an 


26 


ANATOMY 


inch  at  its  lower  end.  It  is  composed  of  three  parts,  the  duodenum, 
about  eight  inches  long,  the  jejunum,  about  seven  and  a  half  feet  long, 
and  the  ileum.  These  parts  are  not  sharply  marked  off  from  each 
other  and  are  not  separated  by  valves.  The  mucous  membrane  of 
the  intestine,  like  that  of  the  stomach,  is  f)rovided  with  tubular  glands, 
the  intestinal  glands,  and  in  addition  its  free  surface  is  thickly  studded 
with  minute  finger-like  processes,  the  villi,  which  serve  to  absorb 
digested  food.  The  muscular  coats  are  the  longitudinal  and  circular, 
and  the  outside  is  covered  by  the  peritoneum  except  for  a  portion  of 
the  duodenum. 


COMMON    BILE    DUCT 


ORIFICE    OF    AC- 
CESSORY    PANCRE- 
ATIC   DUCT 
ORIFICE    OF    BILE 
AND    PANCRE- 
ATIC   DUCTS 


SUP     MESENTERIC 
ARTERY 


Fig. 


-Ducts  of  the  pancreas.     Part  of  the  front  wall  of  the  duodenum  is  cut 
away.     (Testut.) 


0.  Large  Intestine  (Fig.  4). — The  passage  from  the  small  to  the  large 
intestine  is  guarded  by  another  sphincter  muscle,  the  ileoceraJ  valve. 
The  large  intestine  is  about  five  feet  in  length  and  two  and  a  half  to 
one  and  a  half  inches  in  diameter.  At  its  ui)per  end  it  extends  past 
the  junction  with  the  ileum  about  two  and  a  half  inches  to  form  a 
blind  pouch,  the  cecum.  The  vermiform  appendix  is  an  extension  of 
the  cecum.  This  organ  is  about  two  inches  in  length  and  has  the 
diameter  of  a  lead-i)encil.  The  colon  proper  begins  at  the  ileum  and 
first  extends  upward  on  the  right  sifle  as  the  ascending  colon,  then 
across  the  abdominal  cavity  as  the  transverse  colon,  then  downward  on 
the  left  side  as  the  descending  colon,  then  toward  the  middle  of  the 


THE  ALIMENTARY  SYSTEM 


27 


body  as  the  sifpiioid  flexure.  The  last  portion,  six  or  eij2;ht  inches  in 
length,  forms  the  rcctinn.  The  mucous  lining  has  no  \illi,  hut  otherwise 
the  coats  are  similar  to  those  of  the  small  intestine.  The  walls  of  the 
cecum  and  coloii  have  a  peculiar  puckered  appearance,  due  to  the  fact 
that  the  longitudinal  muscles  are  arranged  in  three  bands  which  are 
shorter  than  the  rest  of  the  wall. 

7.  Anus. — The  lower  opening  of  the  intestine  is  lined  with  ectoderm 
and  is  guarded  by  two  sets  of  muscles,  the  internal  and  external 
sphincters. 

8.  Salivary  Glands. — Described  in  the  chapter  on  Special  Anatomy. 


Fig.  6. — The  liver,  front  view.     (Drawn  from  the  His  cast.     Gerrish.) 


9.  The  Pancreas  (Fig.  5). — The  pancreas  is  a  gland  of  irregular  form, 
about  six  inches  long,  two  inches  wide,  and  one-half  inch  thick,  which 
lies  transversely  behind  and  below  the  stomach.  In  weight  it  varies 
from  tw'o  to  three  ounces.  Its  right  end  lies  in  the  curve  of  the  duo- 
denum and  its  duct  enters  the  duodenum  along  with  that  of  the  liver, 
two  or  three  inches  below  the  pyloric  valve.  It  is  the  most  important 
digestive  gland  of  the  body,  since  its  secretion,  the  pancreatic  juice, 
acts  on  all  kinds  of  foods.  The  pancreas  also  contains  numerous  duct- 
less glands  (glands  of  internal  secretion)  about  one  twenty-fifth  of 
an  inch  in  diameter,  the  islands  of  Langerhans,  which  secrete  important 
fluids  into  the  blood. 


2S 


ANATOMY 


10.  The  Liver  (Fig.  6). — This  organ  weighs  between  fifty  and  sixty 
ounces  and  is  therefore  much  the  largest  gland  of  the  body.  It  lies 
close  lip  against  the  diaphragm  on  the  right  side  and  middle  of  the 
abdominal  cavity,  and  covers  the  small  end  of  the  stomach,  the  upper 
part  of  the  ascending  colon  and  the  right  kidney.     It  is  very  irregular 


Fig.  7. — Diagram  presenting  the  structure  of  the  human  small  intestine.  (Bohm, 
Davidoff,  and  Mall;  slightly  modified.)  Two  villi  are  represented.  In  the  one  on  the 
left  the  bloodvessels  are  shown;  in  the  one  on  the  right,  the  lymphatics.  The  line  .S 
indicates  the  surface  of  the  mucous  membrane  between  the  villi,  a,  central  la(!teal 
vessel;  h,  smooth  muscular  fibers  extending  into  the  villus  from  the  muscularis  mucosie; 
c,  lymphadenoid  tissue  beneath  the  epithelial  covering  of  the  villus;  d,  crypt  of  Lieber- 
kiihn;  e,  tunica  proi)ria  of  lymphadenoid  tissue,  and  continuous  with  that  of  the  villus; 
f,  muscularis  rnuc(jsic,  forming  the  deepest  portion  of  the  mucous  membrane;  o<  svi\)- 
mucosa  containing  the  larger  bloodvessels  and  the  lynii)hatic  plexus,  h;  i,  encircling  layer 
of  the  muscular  coat;  j,  longitudinal  layer;  k,  lymphatic  plexus  within  the  must'ular 
coat;  I,  serous  coat;  m,  vein.  The  crypts  are  lined,  and  the  villi  covered,  with  colunmar 
epithelium.     (Dunham.) 


in  form  and  consists  oi  five  lobes.  It  is  held  in  place  hy  five  ligaments. 
The  sub.stance  of  the  liver  c-onsists  of  the  glandular  cells  arranged  in 
lobules  a  little  larger  than  the  head  of  a  pin.  The  hepatic  arterij 
carries  pure  blood  to  nourish  the  liver,  and  the  portal  vein  carries  a 
large  supply  of  blood  to  it  from  the  intestinal  tract  to  be  worked  over 
by  the  liver  before  it  returns  to  the  general  circulation.    The  hepatic 


THE  ALIMENTARY  SYSTEM 


29 


vein  returns  the  blood  from  both  sources  to  the  heart.  The  bile 
ducts  arise  among  the  Hver  cells  and  join  to  form  the  hepatic  duct. 
This  unites  with  the  cystic  duct  of  the  (/all-hJadder  to  form  the  common 
bile  duct  which  enters  the  intestine  along  with  the  pancreatic  duct. 
The  (/(dl-bladder  is  a  sac  lying  in  a  depression  on  the  under  side  of  the 
right  lobe  of  the  liver.  It  serves  as  a  reservoir  for  the  bile  secreted 
between  periods  of  digestion. 

Histology  of  the  Intestinal  Tract. — The  tissues  which  enter  into  the 
formation  of  the  intestinal  tube  are  arranged  in  the  form  of  layers  or 
coats,  and,  with  slight  differences,  are  similar  throughout.  The  inner 
coat,  next  to  the  cavity,  consists  of  mucous  membrane  (Fig.  7,  A)  made 
up  of  a  single  layer  of  cells  backed  up  by  loose  connective  tissue  in 
which  small  tubular  glands  are  imbedded.     In  the  stomach  the  mucous 


MOUTHS    OF    GLANDS 
OF    LICBERKUHN 


SOLITARY   GLAND 


Fig.  8. — Free  surface  of  the  mucous  membrane  of  the  small  intestine,  showing  villi, 
solitary  glands,  and  openings  of  the  intestinal  glands.     Semidiagrammatic.     (Testut.) 


membrane  is  not  smooth,  as  it  is  in  the  mouth  and  gullet,  but  is 
thrown  into  irregular  folds  which  are  less  pronounced  as  the  stomach 
becomes  filled.  In  the  small  intestine,  in  addition  to  circular  folds, 
there  are  the  small  finger-like  processes  already  described  as  the  dilli 
(Fig.  8).  In  the  large  intestine  both  the  circular  folds  and  the  villi 
are  lacking. 

Outside  of  the  mucous  layer  is  the  submucous  coat  (Fig.  7,  B)  con- 
sisting of  loose  connective  tissues  in  which  are  distributed  bloodvessels, 
lymphatics,  and  the  nerves  of  the  intestinal  (Meissner's)  plexus. 
Lymph  glands  (Peyer's  patches  and  solitary  nodules)  are  imbedded  in 
this  laye;*. 

Next  are  found  the  muscular  coats  (Fig.  7,  C),  the  inner  circular  and 
the  outer  longitudinal,  with  the  nerves  of  the  plexus  myentericus 


30  ANATOMY 

between.  In  the  stomach  a  third  muscular  coat  with  obhque  fibers 
occurs  inside  of  the  circular  coat.  These  muscles  are  responsible  for 
the  movements  of  the  intestinal  tube  in  handling  the  food.  At  various 
places  along  the  tube  the  circular  muscles  are  increased  in  size  to  form 
the  sphincter  muscles  already  mentioned  which  govern  the  passage  of 
food  from  one  part  to  another. 

The  outside  layer  of  the  tube  is  the  peritoneum  (Fig.  7,  D),  a  layer 
of  serous  membrane  which,  by  its  smooth  secretions,  prevents  friction 
when  the  various  parts  come  in  contact. 

The  intestine  and  stomach  are  held  in  place  by  a  thin  membrane 
of  connective  tissue  (the  mesentery),  which  is  attached  along  the  mid- 
line of  the  back  wall  and  this  tissue,  as  well  as  the  inner  wall  of  the 
body  in  the  abdominal  region,  is  covered  by  the  peritoneum.  A  broad 
fold,  the  great  omentum,  also  covered  with  peritoneum,  extends  down- 
ward between  the  intestines  and  the  front  wall  of  the  bod}^  for 
further  prevention  of  friction. 

THE   RESPIRATORY   SYSTEM. 

The  two  chief  functions  of  the  respiratory  system  are  to  supply 
oxygen  to  the  body  and  to  remove  carbon  dioxide  which  accumulates 
in  the  body  as  the  result  of  oxidation  or  combustion  within  the  cells. 
All  the  cells  of  the  body  are  concerned  in  the  use  of  oxygen  and  con- 
sequently in  the  formation  of  carbon  dioxide,  and  the  fluids  of  the  body, 
blood  and  lymph,  are  concerned  in  the  distribution  of  oxygen  and  in 
collecting  the  carbon  dioxide  preparatory  to  elimination.  The  respira- 
tory system  is  thus  left  with  only  the  work  of  delivering  oxygen  to  the 
blood  and  the  removal  of  carbon  dioxide.  The  primary  apparatus 
for  this  purpose  consists  of  the  moist  membrane  lining  the  air  sacs  of 
the  lungs,  but  accessory  structures  are  necessary  for  carr;)'ing  the  air 
to  and  from  the  absorptive  area  of  the  lungs.     These  are  as  follows: 

1.  External  nares. 

2.  Xasal  passages. 

3.  Internal  nares. 

4.  Pharynx. 

5.  Glottis. 
G.  Larynx. 
7.  Trachea. 

S.  Bronchi  and  bronchioles. 

0.  Air  sacs  or  alveoli. 
In  breathing  the  air  enters  these  passages  in  the  order  given  and 
passes  out  in  the  reverse  order.  The  nares,  nasal  ])assages  and  pharynx 
will  be  discussed  elsewhere.  The  glottis  is  the  opening  from  the 
pharynx  into  the  larynx.  This  opening,  in  the  mammals,  is  provided 
with  a  hinged  cartilaginous  lid  or  Haj),  the  rijigJottis  (Fig.  9),  which 
closes  the  ojx'uing  in  the  act  of  swallowing,  thus  pn^x'cnting  the  entrance 
of  food  or  water  to  the  air  jjassages.     The  larynx  (Fig.  10),  or  voice 


THE  RESPIRATORY  SYSTEM 


31 


box,  is  an  expansion  of  the  passage  and  consists  of  two  special  cartilages, 
the  cricoid  and  arytenoid,  by  which  the  vocal  cords  can  be  regulated 
in  the  production  of  the  voice.  These  cords  are  situated  at  the  middle 
of  the  larynx  in  such  a  manner  that  they  ordinarily  permit  the  free 


Superior  cornu 


Inferior  cornu. 


Fig.  9. — Front  view  of  cartilages  of  larynx,  trachea,  and  bronchi.     (Gray.) 


passage  of  the  air  in  breathing,  but  when  stretched  by  the  action  of 
the  laryngeal  muscles  upon  the  cartilages  they  approach  each  other 
and  more  nearly  close  the  opening,  when  they  are  thrown  into  vibra- 
tions by  the  passage  of  the  air. 


32 


ANATOMY 


The  trachea  (Fig.  9),  or  windpipe,  is  a  tube  from  four  to  five  inches 
long  and  about  three-quarters  of  an  inch  in  diameter,  which  extends 
downward  into  the  thorax  or  chest  between  the  hmgs,  where  it  divides 
into  the  right  and  left  bronchi.  Its  walls  consist  of  fibrous  connective 
tissue  and  muscles,  in  which  is  imbedded  a  series  of  incomplete  carti- 
laginous rings.  These  partial  rings,  with  their  opening  behind  and 
next  to  the  esophagus,  serve  to  keep  the  passage  open  for  the  free 
entrance  of  the  air.  The  trachea,  like  the  other  air  passages,  is  lined 
with  mucous  membrane  and  this  membrane  is  provided  with  cilia 
or  vibratile  threads  of  protoplasm  which  constantly  beat  in  an  upward 
direction  to  sweep  out  any  impurities  brought  by  the  respiratory 
current.  The  right  and  left  hronchi  enter  their  respective  lungs  and 
break  up  into  large  numbers  of  bronchioles  or  bronchial  tubes,  which 
have  much  the  same  structure  as  the  trachea,  but  become  thinner- 
walled  as  they  become  smaller  and  approach  the  air  sacs. 


APEX    OF    SUP.    HORN    OF 
THYROID    CARTILAGE 


CORN    CULUM 

AR     gcis 

U    lEIFORM 
CURTILAGE 
ARYTENO  EPIGLOT- 
TIDIAN    FOLD 

\APEX    OF    GREAT 
\   HORN    OF    HYOID 


LATERAL    GLOSSO- 
EPIGLOTTIDIAN    FOLD 


MIDDLE    GLOSSO- 
EPIGLOTTIDIAN    FOLD 


Fig.  10. — Larynx,  viewed  from  above.     (Testut.)  - 


The  Lungs  (Plate  I)  are  essentially  composed  of  the  air  .sacs  or 
alveoli,  wiiicli  arc  present  in  such  enormous  munbers  that  their  com- 
bined surface  is  equal  to  about  eight  hundred  times  the  surface  of  the 
body.  Thus  it  is  not  difficult  to  understand  why  they  are  such  efficient 
organs  for  the  exchange  of  gases.  Each  alveolus  is  lined  with  a  thin 
layer  of  cpitlielial  cells  of  the  mucous  membrane.  The  })lood,  in  the 
pulmonary  capillaries,  is  richly  supplied  to  the  alveoli,  so  that  in 
making  the  exchange  the  gases  have  only  to  pass  through  the  thin 
walls  of  tlie  cai)illaries  and  the  muctous  membrane.  The  lungs  occupy 
nearly  all  the  space  in  the  thoracic  or  chest  cavity,  except  that  occu- 
pied by  the  heart.     The  right  lung  is  slightly  larger  than  the  left  and 


PLATE  I 


PLEURA 


DiagraiTi  of  a  Lobule  of  ihe   Lung. 

A  bronchiole  is  seen  dividing  into  two  branches,  one  of  which  runs  upward  and  ends  in  the 
lobule.  In  the  lobule  are  four  groups  of  infundibula.  At  the  left  are  two  infundibula,  the 
alveoli  of  which  present  their  outer  surfaces.  Next  are  three  infundibula  in  vertical  section, 
the  alveoli  of  each  opening  into  the  common  passageway.  Upon  the  ultimate  bronchiole  of  this 
group  arc  alveoli.  In  the  next  group  the  first  infundibulum  shows  a  pulmonary  arteriole  sur- 
rounding the  opening  of  each  alveolus,  and  the  second  gives  the  same  with  the  addition  of  the 
close  capillary  network  in  the  wall  of  each  alveolus.  The  same  arrangement  of  vessels  is  seen 
in  the  alveolus  upon  the  bronchiole  of  this  group.  Around  the  fourth  group  is  a  deep  deposit 
of  pigment,  such  as  occurs  in  old  age,  and  in  the  lungs  of  those  who  inhale  coal-dust  and  the 
like.  On  the  bronchiole  lies  a  branch  of  the  pulmonary  artery  (blue),  bringing  blood  to  the 
infundibula  for  aeration.  It  also  supplies  nourishing  blood  to  the  tubes  and  other  structures 
within  the  lobule.  Beginning  between  the  infundibula  are  the  radicles  of  the  pulmonary  vein 
(red),  a  root  of  which  lies  upon  the  bronchiole.  The  lironchial  artery  is  shown  as  a  small  vessel 
bringing  nutrient  blood  to  the  bronchiole  (outside  of  the  lobule),  the  artery  and  vein,  and  all 
of  the  structures  between  and  around  the  lobule.  No  attempt  is  made  to  show  the  sustentacular 
tissue  which  occupies  the  spaces  within  and  around  the  lobule.      (Gerrish.) 


THE  CIRCULATORY  SYSTEM  33 

is  composed  of  three  lobes,  upper,  middle,  and  lower,  while  the  left 
lung  has  only  upper  and  lower  lobes.  The  outer  surface  of  the  lungs 
and  the  inner  surface  of  the  chest  wall  are  covered  by  the  pleura,  a 
smooth  serous  membrane  which  effectually  prevents  friction  during 
the   respiratory   mo\'ements. 

The  Chest  Wall. — In  order  to  bring  the  air  into  the  lungs  it  is  neces- 
sary that  the  chest  cavity  be  enlarged.  This  is  done  rhythmically  by 
means  of  muscles.  The  diaphragm,  which  has  already  been  mentioned 
as  a  partition  separating  the  abdominal  from  the  chest  cavit}^  is  a 
broad,  thin  sheet  of  muscle  closing  off  the  lower  part  of  the  chest 
and  at  rest  is  curved  upward,  somewhat  like  ^n  inverted  bowl.  When 
in  action  the  fibers  of  this  muscle  contract  so  as  to  make  the  diaphragm 
nearly  flat,  thus  increasing  the  space  above  it.  Also  the  external 
intercostal  muscles,  running  from  rib  to  rib,  raise  the  ribs  and  so  increase 
the  diameter  of  the  chest.  The  thoracic  cavity  is  thus  enlarged  in  a 
vertical  direction  by  lowering  the  diaphragm  and  in  a  transverse 
direction  by  the  action  of  the  intercostal  muscles.  As  the  air  passages 
are  normally  open  the  outside  air  rushes  in  to  fill  the  partial  \acuum 
created  by  enlarging  the  chest  cavity.  No  special  apparatus  is  ordi- 
narily required  for  the  expulsion  of  the  air,  for  the  abdominal  wall  has 
been  pushed  outward  by  the  action  of  the  diaphragm  and  the  chest 
wall  has  been  stretched  by  the  action  of  the  intercostal  muscles,  and 
when  the  muscular  force  is  released  the  collapse  of  the  abdominal 
and  chest  walls  forces  out  the  air  from  the  lung.  In  rapid  or  forced 
breathing,  however,  the  internal  intercostal  muscles  forcibly  contract 
the  chest  wall  to  hasten  the  process.  In  forced  inspiration  other 
muscles  than  those  mentioned,  attached  to  the  upper  part  of  the  chest, 
may  be  brought  into  action. 

THE   CIRCULATORY    SYSTEM. 

This  system  consists  of  a  pumping  organ,  the  heart,  and  a  set  of 
conducting  tubes,  the  arteries,  capillaries,  veins,  and  lymphatics, 
through  which  the  fluids  of  the  body  are  distributed  to  carry  oxygen 
and  foods  to  the  ^'arious  tissues  and  to  collect  the  wastes  and  deliver 
them  to  the  excretory  organs. 

The  Heart. — The  heart  is  a  double  muscular  organ  with  four  cham- 
bers, two  auricles  and  two  ventricles,  which  is  lodged  in  a  serous  sac, 
the  pericardium,  in  the  lower  part  of  the  chest  cavity  nearly  in  the 
midline.  (See  Plate  II.)  We  are  accustomed  to  think  of  the  heart 
as  lying  on  the  left  side  because  its  beat  is  felt  most  strongly  there. 
The  apex  of  the  heart  is  tipped  toward  the  left  and  also  projects 
forward  so  that  it  comes  nearest  to  the  surface  just  at  the  left  of  the 
breast-bone  below  the  fifth  rib.  Though  the  right  and  left  sides  of 
the  heart  really  function  separately,  they  are  bound  together  in  such 
a  manner  that  they  act  simultaneously.  The  right  auricle  receives  the 
blood  from  the  system  and  pumps  it  into  the  right  ventricle  which  in 
3 


34  ANATOMY 

turn  pumps  it  to  the  lungs  (pulmonary  circulation).  The  left  auricle 
receives  the  blood  from  the  lungs  and  delivers  it  to  the  left  ventricle 
which  sends  it  out  to  all  parts  of  the  body  (systemic  circulation). 
Because  of  the  much  greater  work  they  have  to  do  the  ventricles  are 
much  thicker  walled  than  the  auricles,  and  for  the  same  reason  the 
wall  of  the  left  ventricle  is  much  thicker  than  that  of  the  right,  since 
it  pumps  the  blood  much  farther. 

The  muscle  cells  of  the  heart  are  of  a  special  kind  (cardiac  muscle). 
They  are  short,  block-like,  and  often  branched,  with  a  single  nucleus 
at  the  center,  with  faint  cross  striations  and  without  cell  walls. 

Between  the  auricles  and  the  ventricles  are  the  auriculoDentrunlar 
valves,  known  on  the  right  side  as  the  tricuspid  and  on  the  left  as  the 
mitral  (Plate  III).  These  are  soft  flaps  of  connective  tissue  which  are 
readily  pushed  out  of  the  way  when  the  blood  is  forced  into  the  ven- 
tricles, but  which  close  the  openings  into  the  auricles  when  the  ven- 
tricles contract.  They  are  held  in  place  when  closed  by  fibrous  cords 
(cJwrdcB  tendonoe)  which  are  provided  with  muscles  at  their  bases 
(papillary  muscles)  so  that  they  are  held  in  the  proper  position  as  the 
ventricles  contract.  The  semihinar  valves  similarly  prevent  the  blood 
from  returning  from  the  arteries  to  the  ventricles.  These  valves  are 
located  at  the  junction  of  the  arteries  with  the  heart.     (See  Plate  II.) 

The  lining  of  the  heart  consists  of  a  delicate  layer  of  flattened  cells, 
which  is  also  continued  as  the  inner  coat  of  the  bloodvessels. 

The  pericardium,  which  encloses  the  heart,  consists  of  a  tough  coat 
of  connective  tissue  lined  by  serous  membrane.  It  is  in  the  form  of  a 
closed,  double-walled  sac,  which  is  so  arranged  that  the  serous  coat 
covering  the  heart  comes  into  contact  only  with  the  serous  lining  of 
the  pericardium,  thus  preventing  friction. 

The  Bloodvessels  (Plate  IV). — The  arteries  are  the  vessels  which 
carry  the  blood  away  from  the  heart.  Their  walls  are  thick  and 
strong  to  withstand  the  pressure  with  which  the  blood  is  forced  into 
them.  At  the  same  time  they  must  be  elastic  enough  to  adapt  them- 
selves to  the  variations  in  pressure  at  different  times.  They  are  made 
up  of  white  fibrous  and  yellow  elastic  connective  tissues,  with  a  layer 
of  muscle  tissue  for  regulating  the  size  of  the  vessel.  Sometimes, 
especially  in  old  age,  the  walls  become  partially  calcified,  causing  the 
condition  known  as  arteriosclerosis.  The  arteries  leave  the  heart  as 
.single  vessels,  the  jjulmoiiari/  artery  from  the  right  ventricle,  the  aorta 
from  the  left. 

The  pulmonary,  going  to  the  lungs,  divides  about  two  inches  from 
the  heart  into  right  and  left  branches  to  enter  the  corresponding 
lungs. 

The  aorta,  emerging  from  the  left  ventricle,  supplies  aerated  l)]o()d 
to  the  whole  body.  The  first  branches  are  the  coronary,  which  return 
at  once  to  supply  the  tissues  of  the  heart  itself.  The  aorta  curves 
backward  above  the  heart  forming  the  arch  and  is  continued  down 
the  posterior  portion  of  the  thoracic  and  abdominal  cavities  as  the 


PLATE   II 


—  LEFT    AURICU- 
LAR   APPENDIX 

r 


LEFT 
VENTRICLE 


The  Pulmonary  Artery  and  Aorta. 

The  front  part  of  the  right  lung  has  been  removed,  and  the  puhiionary 
vessels  and  the  bronchial  tubes  are  thus  exposed.     (Gerrish.) 


PLATE  III 


Valves  of  the  Heart  and  Great  Arteries,  Viewed  froni  Above,  the 
Auricles  having  been  Removed.     (Gerrish.) 


PLATE   IV 


Facial 


Innominate 


Heart 


Aorta - 


Common  iliac 


External  ili>»'^' 
Internal  ili;ic 


Temper"! 

external  carotid 
Common  carotid 
Subclavian 
Aorta 


■\xilbry 


Urachial 


The  Principal  Arteries  and  Veins  of  the  Body.     (Morrow. 


tup:  CIRCl'LATOIiY  SYSTKM  'Afi 

descend i II (/  aorta.  From  the  arch  are  given  oil'  the  iitnoiiiuiaic  artery 
which  divides  at  once  into  the  right  common  carotid  and  right  sub- 
clavian. The  left  common  carotid  and  left  subclavian  arteries  are 
given  ofi'  separately  from  the  arch  of  the  aorta.  The  suhclavians 
supply  the  arms.  The  common  carotids  divide  to  form  the  internal 
carotids,  distributed  to  the  brain  and  eyes,  and  the  external  carotids 
which  divide  to  supply  with  blood,  the  structures  of  the  oral  cavity, 
tongue,  throat,  face,  and  the  outer  ])art  of  the  head.  The  descending 
aorta  gives  oti"  many  branches,  one  of  which  goes  to  the  lungs  to  supply 
them  with  food  and  oxygen.  The  important  abdominal  arteries  are 
the  celiac  axis  supplying  the  stomach,  liver,  spleen,  and  pancreas; 
the  superior  mesenteric  supplying  the  small  intestine  and  half  of  the 
large  intestine;  the  inferior  mesenteric  supplying  the  lower  half  of 
the  large  intestine,  and  the  renals  supplying  the  kidneys.  The  abdomi- 
nal aorta  divides  at  its  lower  end  into  the  right  and  left  iliac  arteries 
which  go  to  the  legs. 

The  Capillaries. — The  arteries  divide  into  smaller  branches,  the 
arterioles,  and  these  continue  to  divide  until  the  smallest  divisions,  the 
capillaries,  are  formed.  These  consist  of  a  single,  flattened  layer  of 
cells,  continuous  with  the  lining  of  the  heart  and  other  vessels.  They 
form  an  exceedingly  fine  network  among  the  tissues  and  the  only  tissues 
lacking  them  are  the  e])ithelia,  the  cartilages,  and  the  cornea  of  the  eye. 

The  Veins. — The  capillaries  unite  to  form  small  venules  which  again 
unite  to  form  larger  and  larger  veins.  Veins  differ  from  arteries  in 
their  thinner  walls,  though  the  same  tissues  are  present,  and  in  the 
fact  that  valves  are  usually  present  which  prevent  any  return  flow  of 
blood,  allowing  it  to  flow  only  toward  the  heart.  In  general  the  veins 
are  nearer  the  surface  than  the  arteries  but  have  a  similar  distribution. 
Thus  the  jugular  veins  return  the  blood  from  the  head,  the  pulmonaries 
from  the  lungs,  etc.  One  notable  exception  is  found  in  the  portal 
vein  (see  Plate  V),  already  mentioned  under  the  liver,  which  collects 
the  blood  that  has  passed  through  the  capillaries  of  the  intestinal 
tract,  carries  it  to  the  liver,  and  there  again  breaks  up  into  capillaries 
among  the  lobules  of  the  liver.  The  hepatic  vein  then  collects  the 
blood  from  both  the  portal  vein  and  the  hepatic  artery  to  return  it  to 
the  heart. 

The  Blood. — The  blood  may  be  considered  a  tissue  in  which  the  inter- 
cellular substance  is  fluid.  This  fluid  is  called  the  plasma  and  consists 
chiefly  of  water  containing  in  solution  the  various  foods  and  wastes 
as  well  as  the  peculiar  <.uh<,t'c\nve ,  fibri nogen ,  which  forms  the  clot  when 
it  escapes  from  the  vessels.  The  cells  are  of  three  sorts,  the  red  cor- 
puscles, the  white  corpuscles  and  the  platelets.  The  red  corpuscles 
(see  Plate  VI)  are  circular,  biconcave  disks  of  protoplasm,  without 
nuclei  or  cell  walls,  but  which  have  the  red  coloring  matter  known  as 
hemoglobin  for  the  transportation  of  oxygen.  These  cells  are  very 
minute,  3^21x0^  of  an  inch  in  diameter,  but  are  so  numerous  that  four  and 
a  half  millions  (in  woman)  to  fi\'e  millions  (in  man)  are  contained  in  a 


36 


ANATOMY 


single  cubic  millimeter  of  blood.     These  corpuscles  are  continually 
being  formed  in  the  red  marrow  of  the  bones. 

The  white  corpuscles,  or  leukocytes  (Plate  VI),  are  of  several  different 
kinds,  but  all  agree  in  being  slightly  granular,  in  having  nuclei  and  in 
possessing  indepenc^ent  motion  and  ability  to  change  their  form 
(ameboid  movement).  They  occur  in  the  lymph  and  other  fluids  of 
the  body  as  well  as  in  the  blood.  They  measure  on  an  average  about 
2X0  0"  of  an  inch  and  are  much  less  numerous  than  the  red  corpuscles. 


Fig.  11. — Lactcals  mid  lymphatics  duriiiy  digestion. 

The  hlood  jjlatrlds  arc  not  well  known.  They  are  irregular  in  form, 
smaller  than  the  red  corpuscles  and  somewhat  less  junncroiis. 

The  Lymphatics  (l^'ig.  11).- — These  vessels  in  a  general  way  follow 
the  .same  cour.se  as  the  veins.  They  carry  back  to  the  general  circula- 
tion the  fluid  part  of  the  blood  which  has  escaped  through  the  thin 


PLATE  V 


Portal  System  of  Veins. 


The   liver  is  turned   upward  and   backward,   and    the  transverse   colon  and    niost 
of  the  small  intestines  are  removed.     (Gerrish. 


PLA.TE  VI 


^.■^ 


eg)     D 

1) 

0' 

i'^ 

Ik               ^.- 

% 

^                  (>^^!■ 

'i^ 

Normal   Blood,  showing  Rouleaux  and  Leukocytes.     (Musser.) 

(Oe.  4,  ob.  1-12   inimersion  )     Dravv-n   l^v  J.   D.  Z.  Cliase. 


THE  EXCRETORY  SYSTEM  37 

walls  of  the  capillaries  to  bathe  the  cells  of  the  various  tissues.  As  the 
pressure  is  greater  in  the  capillaries  the  fluid,  once  escaped,  cannot 
return  to  the  blood  directly,  but  is  carried  back  by  another  set  of 
vessels.  These  differ  but  little  from  the  veins  except  that  they  are 
thinner  walled.  The  lymph  itself  differs  but  little  from  the  plasma  of 
the  blood,  except  that  it  contains  less  food  and  oxygen  and  more 
carbon  dioxide  and  other  waste  matter.  There  are  two  large  lymphatic 
vessels  which  pour  the  lymph  back  into  the  blood  by  way  of  the  jugular 
veins  just  under  the  collar-bones.  The  right  vessel  is  small  because 
it  collects  only  the  lymph  from  the  right  arm  and  shoulder  and  the 
right  side  of  the  head.  The  left  vessel  collects  the  lymph  from  the 
corresponding  areas  and  also  from  all  the  lower  part  of  the  body.  A 
large  vessel,  known  as  the  thoracic  duct,  brings  up  to  the  left  jugular 
vein  all  the  lymph  from  the  abdominal  region  and  the  lower  limbs. 
The  lymphatics  of  the  intestinal  region  have  a  special  function  in 
absorbing  the  fatty  portions  of  the  digested  food.  This  passes  into 
these  vessels  in  the  form  of  an  emulsion  of  a  milky  color,  and  this 
fact  has  given  to  the  particular  lymphatics  carrying  this  fluid  the  name 
of  lacteals.  Along  the  line  of  the  lymphatic  vessels  are  found  the 
lymph  nodes  or  glands,  in  which  the  white  corpuscles  are  formed.  They 
are  very  numerous  and  widely  distributed. 

THE   EXCRETORY    SYSTEM. 

The  elimination  of  wastes  formed  in  the  body  is  carried  on  to  some 
extent  by  the  lungs,  which  remove  practically  all  the  carbon  dioxide, 
the  skin,  the  liver,  and  the  intestinal  epithelium,  but  the  special  S3'stem 
evolved  for  the  remo^'al  of  the  non-volatile  wastes  is  that  known  as 
the  excretory  system.  The  essential  organs  of  this  system  are  the 
kidneys,  and  the  accessory  organs  are  the  ureters,  bladder,  and  urethra. 

The  Kidneys  (Fig.  12). — The  kidneys  are  compound  tubular  glands, 
somewhat  bean-shaped,  situated  on  either  side  of  the  midline  behind 
the  peritoneum  with  the  concave  side  (hilum)  toward  the  midline,  and 
the  middle  of  each  kidney  is  a  little  above  the  waist  line.  The  right 
kidney  is  a  little  lower  than  the  left,  to  make  room  for  the  liver.  Each 
kidney  is  about  four  inches  long  by  two  broad  and  one  in  thickness, 
and  averages  about  five  ounces  in  weight.  On  the  outside  of  the 
kidney  is  a  tough  capsule  of  connective  tissue.  Inside  of  this  is  a  thick 
layer  known  as  the  cortex  which  is  the  chief  secreting  portion.  Toward 
the  center  from  this  there  is  still  another  layer,  the  medulla,  which  is 
thrown  up  into  a  number  of  pyramidal  projections,  the  pyramids  of 
Malpighi.  There  remains  a  central  cavity,  the  j^ehis  (basin)  of  the 
kidney.  This  chamber  serves  to  collect  the  urine  which  is  poured  into 
it  from  the  countless  tubules.  From  the  pelvis  the  urine  is  passed  out 
into  the  ureter  to  be  carried  to  the  bladder. 

The  essential  structures  of  the  kidneys  are  the  uriniferous  tubules 
which   are   estimated   to   number   about   500,000.     On   examination 


38 


ANATOMY 


under  the  microscope  the  tubule  (Fig.  13)  is  found  to  consist  of  an 
irreguhirly  coiled  portion,  one  part  of  Avhich  is  a  straight  loop  and 
of  an  inflated  terminal  portion,  the  Bowman  capsule.  This  capsule 
contains  a  knot  of  capillary  bloodvessels  known  as  the  glomerulus.  The 
capsule  and  glomerulus  together  constitute  the  Malpighian  corpuscle. 
The  cavity  of  the  capsule  is  continuous  with  that  of  the  tubule.  This 
latter  structiu'e  is  formed  of  glandular  cells  for  the  purpose  of  secretion 
and  the  cells  vary  somewhat  in  different  portions  of  the  tubule.  Each 
tubule  terminates  in  a  collecting  tubule  which  gathers  the  secretions 
from  a  number  of  the  uriniferous  tubules.  The  collecting  tubules 
open  upon  the  surface  of  the  pyramids  and  pour  the  urine  into  the 
pelvis  of  the  kidney. 


Fig.  12. — Vertical  section  of  kidney.     (Gray.) 


The  kidneys  are  abundantly  sui)i)H('d  with  blood  from  the  renal 
arteries.  After  the  blood  has  passed  through  the  cai)illaries  of  the 
glomeruli  and  about  the  secreting  tubules  it  is  returned  to  the  circula- 
tory system  by  way  of  the  renal  veins. 

The  Ureters. — The  ureters  are  the  ducts  of  the  kidneys.  They  are 
about  the  diameter  of  a  goose-quill  and  a  foot  or  more  in  length.  Their 
walls  are  muscular  for  the  purpose  of  forcing  the  urine  into  the  bladder. 

The  Bladder. — The  bladder  is  merely  a  reservoir  for  the  urine.  It  is 
lined  witli  a  mucous  membrane  which  is  continuous  with  that  of  the 


THE  EXCRETORY  SYSTEM 


39 


ureters  and  urethra.     The  wall  is  chiefly  made  up  of  muscle  and  con- 
nective tissues.     Oil  the  outside  it  is  covered  by  the  peritoneum.     The 


Fig.  13. — Diagram  of  three  uriniferous  tubules  and  their  relation  to  a  collecting  tubule: 
A,  beginning  of  a  tubule,  the  Malpighian  corpuscle  of  which  is  situated  in  the  lowermost 
portion  of  the  cortex;  B,  about  the  middle  of  the  cortex;  C,  in  the  outer  portion  of  the 
cortex;  m,  Malpighian  corpuscle;  v,  vessel  porta;  n,  neck;  pc,  proximal  convoluted 
portion;  es,  end  segment;  dl,  descending  limb;  al,  ascending  limb  of  the  loop  of  Henle; 
dc,  distal  convoluted  portion;  j,  junctional  tubule;  c,  collecting  tubule.     (Huber.) 


40 


ANATOMY 


ureters  enter  the  bladder  near  its  base  by  a  very  diagonal  course.  At 
the  neck  of  the  bladder  is  a  sphincter  muscle  which  is  normally  closed 
and  opens  only  in  the  act  of  micturition.  The  duct  of  the  bladder  is 
the  urethra. 


EPIDERMIS 


PAPILLA    OF 
DERMIS 


SUBCUTANEOUS 
AREOLAR    TISSUE 


MALPIGHIAN 
LAYER 


DUCT    OF    SEBA- 
CEOUS   GLAND 


SEBACEOUS 
GLAND 


ROOT    OF    HAIR 


HAIR     FOLLICLF. 
ADIPOSE    TISSUE 


GLOMERULUS    OF 
SWEAT    GLAN  D 


BULB    OF    HAIR 
PAPILLA    OF    HAIR 


Iarrector   pili 
Fig.  14. — Vertir-al  section  of  the  skin.     (Tcstut.) 


THE    SKIN. 

This  organ  is  by  no  means  a  simple  structure,  but  consists  of  the 
following  parts  (Fig.  14): 

1.  Cuticle  or  epidermis. 

2.  Cutis  or  dermis. 

3.  Sweat  glands. 

4.  Oil  glands. 

o.  Hairs  and  nails,  appendages  of  the  skin. 
1.  The  epidermal  tissue  or  cuticle  forming  the  outer  or  scarf  skin 
consists  of  layers  of  cells  that  are  dead  on  the  outside  and  fall  oil' 
continually  in  great  numbers.  These  are  replaced  by  others  which 
are  constantly  being  formed  in  the  lower  layer  next  to  the  cutis.  The 
epiflcrmis  has  no  nerves  and  receives  no  blood,  but  obtains  its  nour- 
ishment from  bloodvessels  which  come  very  close  to  it  in  the  cutis  and 
the  l\'mph  j;enetrates  it  to  nourish  the  living  cells. 


DUCTLESS  GLANDS  41 

2.  The  Cutis. — The  cutis  or  inner  or  true  skin  (derma)  is  composed 
chiefly  of  white  fibrous  and  yellow  elastic  connective  tissues  closely 
interwoven  to  form  an  extremely  tough  and  ])lial)le  layer.  In  this 
are  embedded  the  bloodvessels,  nerves,  and  muscles  of  the  skin. 

3.  Bloodvessels. — These  are  very  numerous  in  the  cutis.  They  not 
only  serve  to  nourish  the  skin,  but  are  of  the  greatest  importance  in 
aiding  in  controlling  the  temperature  of  the  body. 

4.  Nerves. — Xerxes  of  several  classes  penetrate  the  cutis  and  have 
their  endings  in  the  walls  of  the  bloodvessels,  in  the  muscles  and  glands, 
or  end  as  sensory  papilla?  of  touch  and  temperature. 

5.  Muscles. — There  is  not  a  great  quantity  of  muscle  tissue  in  the 
skin,  but  at  the  base  of  'every  hair  (and  even  though  the  human  body 
seems  to  be  naked  over  the  greater  part  of  its  surface  there  are  minute 
hairs  thickly  imbedded  in  the  skin)  there  is  a  little  muscle  which  is 
able  to  contract  and  set  the  hair  on  end.  In  cold  weather  these  muscles 
contract  the  skin,  which  is  roughened  on  the  outside  as  a  result  of  the 
reaction  of  the  muscles  on  the  vestigial  hairs,  the  phenomenon  being 
known  as  "goose  flesh." 

6.  Sweat  Glands. — The  minute  glands  which  secrete  the  perspira- 
tion arise  from  the  epidermis,  but  they  are  deeply  imbedded  in  the 
cutis.  They  open  as  the  microscopic  pores  of  the  skin,  below  which 
they  have  the  form  of  spiral  tubules  and  end  near  the  lower  part  of  the 
cutis  in  a  coiled  knot. 

7.  Oil  Glands. — These  also  belong  to  the  epidermis,  though  imbedded 
in  the  cutis.  They  are  found  in  connection  with  the  hair  follicles. 
Even  though  the  hairs  are  microscopic  the  glands  are  present  and 
secrete  the  sebaceous  matter  which  keeps  the  skin  soft. 

8.  Areolar  Tissue. — This  tissue  is  composed  of  connective  tissues 
similar  to  those  which  make  up  the  cutis,  but  the  fibers  are  loosely 
woven.  This  layer  lies  below  the  cutis,  which  it  attaches  more  or  less 
loosely  to  the  organs  beneath. 

9.  Adipose  Tissue. — This  is  fatty  tissue,  some  of  which  is  nearlj^ 
always  present  in  the  areolar  tissue  just  below  the  cutis.  In  reality 
it  is  composed  of  areolar  tissue,  in  the  cells  of  which  fat  globules  are 
stored.  It  occurs  frequently  in  other  parts  of  the  body  in  connection 
with  areolar  connective  tissue. 

DUCTLESS    GLANDS. 

A  number  of  glands  are  without  ducts  and  deliver  their  secretions 
to  the  blood  (ductless  glands  or  glands  of  internal  secretion) .  Although 
these  work  together  to  some  extent  in  controlling  the  metabolism  of 
the  body,  they  are  not  usually  considered  as  forming  a  system,  because 
they  are  scattered  about  the  body  and  usually  have  no  connection  with 
each  other.  Their  secretions,  called  hormones,  are  chemical  regulators 
of  the  body  and  are  of  such  great  importance  that  the  removal  of  the 
glands  is  often  foUow^ed  by  death  or  at  least  by  grave  disturbances 
in  the  metabolism  of  the  body. 


42  ANATOMY 

1.  Thyroid  Gland. — This  gland  lies  in  the  neck  on  either  side  of  the 
trachea,  just  at  the  lower  end  of  the  larynx.  It  is  deep  red  in  color  and 
weighs  about  one  ounce.  Enlargement  of  this  gland  is  known  as 
goitre. 

2.  Parathyroid  Glands. — These  are  two  small  masses  of  cells,  about 
a  quarter  of  an  inch  in  diameter,  imbedded  in  the  surface  of  the  thyroid. 
On  accoiuit  of  their  small  size  and  their  position  they  were  not  known 
until  comparati\'ely  recently.  Functionally  they  have  nothing  to  do 
with  the  th\Toid,  but  are  quite  separate  organs. 

3.  Thymus  Gland. — This  organ  is  situated  within  the  chest  cavity, 
above  the  heart  and  in  front  of  the  trachea.  It  appears  very  early  in 
fetal  life,  functions  during  childhood,  but  has  almost  entirely  disap- 
peared at  puberty.  iVt  its  largest  it  weighs  about  three-quarters  of 
an  ounce. 

4.  The  Adrenal  or  Suprarenal  Glands. — The  adrenal  or  suprarenal 
glands  are  two  bodies,  each  weighing  about  an  eighth  of  an  ounce, 
lying  one  above  each  kidney  (Fig.  12).  In  addition  to  gland  cells  they 
contain  much  nervous  tissue. 

5.  The  Hypophysis  or  Pituitary  Body. — The  hypophysis  is  lodged 
within  the  skull  beneath  the  midbrain,  to  which  it  is  attached. 

6.  The  Spleen. — The  spleen  is  the  largest  of  the  ductless  glands.  It  is 
situated  behind  the  stomach  on  the  left  side  of  the  body.  It  has  a 
dark  red  color  and  weighs  from  five  to  eight  ounces.  This  gland  also 
varies  according  to  age,  being  larger  in  youth.  It  is  well  supplied 
with  blood  and  contains  a  large  amount  of  lymphoid  tissue.  After 
prolonged  attacks  of  malaria  the  spleen  becomes  permanently  enlarged, 
forming  the  condition  known  as  "ague  cake." 

Other  ductless  glands,  which  are  minute  and  which  are  little  known 
as  far  as  their  functions  are  concerned,  are  the  pineal  hudy  arising 
from  the  roof  of  the  midbrain,  the  coccygeal  gland  near  the  tip  of  the 
coccyx  and  the  carotid  glands  situated  at  the  upper  ends  of  the  common 
carotid  arteries. 

While  the  above  glands  apparently  function  only  as  ductless  glands, 
there  are  other  structures  in  the  body,  which,  in  addition  to  other 
functions,  secrete  hormones  to  the  blood.  Among  these  are  the 
liver,  the  pancreas  (islands  of  Langerhans),  the  reproductive  organs,  the 
lymph  glands,  and  the  mucous  membrane  of  the  intestinal  wall. 

THE    SKELETAL    OR    SUPPORTING    SYSTEM. 

h\  the  broadest  sense  this  includes  all  the  sui)])()rting  structures  of 
the  body,  which  fall  into  the  following  classes: 

1.  P'ibrous  connective  tissues. 

2.  Tendons. 

3.  Ligaments. 

4.  Cartilages. 

5.  Bones. 


THE  SKELETAL  OR  SUPPORTING  SYSTEM  43 

The  skeleton  proper  consists  of  the  bones  and  the  cartilages  con- 
nected with  them,  hut  the  connective-tissue  fibers  that  bind  together 
the  soft  cells  of  other  tissues  are  just  as  truly  supi)orting  in  their 
function  and  form  for  those  tissues  a  skeletal  structure  that  is  just  as 
real  as  is  the  bony  framework  for  the  body  as  a  whole. 

1.  The  Connective  Tissues. — The  connective  tissues  have  already  been 
described  as  consisting  of  white  inelastic  and  yellow  elastic  fibers 
which  are  interlaced  among  the  cells  of  other  tissues  all  over  the  body 
except  in  the  epithelium,  and  even  in  this  case  we  find  that  the  cells 
are  underlaid  by  a  structure,  known  as  the  basement  membrane,  formed 
by  connective  tissue. 

2.  Tendons. — Tendons  have  already  been  mentioned  as  forming  the 
connection  between  muscles  and  the  structures  which  they  move. 

3.  Ligaments. — Ligaments  consist  of  bundles  of  inelastic  fibers  and 
serve  to  bind  the  bones  together  at  the  joints  and  to  hold  other  organs, 
as  the  liver  and  ovaries,  in  place. 

4.  Cartilages. — Cartilages  or  gristles  as  they  are  more  commonly 
called,  are  characterized  by  their  tough,  elastic  nature.  They  are 
known  as  (1)  hyaline,  when  pure;  (2)  fibrocartilage,  when  mixed  with 
white  fibrous  tissue;  and  (3)  yellow  elastic  cartilage,  when  mixed  with 
yellow  elastic  fibers. 

As  a  rule  the  cartilages  are  disposed  in  certain  definite  relations  to 
the  bones,  either  between  the  joints  to  absorb  shock,  which  is  the  usual 
arrangement,  or  as  in  the  attachment  of  the  ribs  to  the  sternum  to  per- 
mit the  expansion  of  the  thorax  in  inspiration.  They  are  also  found 
in  the  external  ear  and  the  tip  of  the  nose,  and  the  sternum  is  pieced 
out  at  its  lower  end  by  the  xiphoid  cartilage.  Rings  of  cartilage 
are  present  in  the  trachea  and  bronchi,  as  already  stated,  to  keep  these 
passages  open. 

Skeleton  (Fig.  15).^ — The  skeleton  or  bony  framework  consists  of 
about  200  to  208  bones.  The  number  varies  within  narrow  limits 
because  certain  small  bones  may  be  present  or  absent  without  making 
any  apparent  difference  in  the  efficiency  of  the  structure. 

Bony  tissue  is  made  up  of  bone  cells,  between  which  there  is  an 
intercellular  substance  of  organic  matter  impregnated  with  lime  salts 
for  the  sake  of  rigidity.  In  young  children  the  bones  are  somewhat 
pliable,  but  in  older  persons  they  become  very  rigid,  owing  to  the 
increasing  deposition  of  lime.  Bone  tissue  is  permeated  by  blood- 
vessels, just  as  other  tissues  are,  for  nourishing  the  cells. 

Around  the  outside,  except  in  the  joints,  there  is  a  tough  connective- 
tissue  layer  called  the  periosteum. 

Bony  tissue  may  be  compact  or  it  may  be  spongy  (cancellous) .  Com- 
pact bone  is  found  in  the  shanks  of  the  long  bones,  such  as  those  of  the 
arms  and  legs,  and  in  the  outer  layer  of  all  other  bones.  vSpongy  bone 
forms  the  mass  of  the  heads  of  the  long  bones,  the  vertebrae  and  ribs, 
the  middle  layers  of  the  skull,  and  so  on.  The  cavities  in  the  middle 
of  the  long  bones  are  filled  with  yellow  marrow,  a  fatty  deposit,  while 


44 


ANATOMY 


the  small  spaces  in  spongy  bone  are  filled  with  red  marroic  within  which 
the  red  blood  corpuscles  are  manufactured.  • 

5.  Bones. — The  bones  fall  naturalh'  into  two  classes,  the  axial  skeleton 
and  the  appendicular  skeleton.  The  former  class  includes  the  bones 
of  the  head,  spinal  column,  ribs  and  sternum,  while  the  latter  class 
consists  of  the  bones  of  the  limbs. 


FRONTAL 
ORBIT- 


.  PARIETAL 

-TEMPORAL 


.CARPUS 
METACARPUS 


Fig.  15. — The  human  skeleton.      (Morrow.) 


The  bones  of  the  head  include  those  of  the  cranium  or  })raiii-case, 
8  in  number,  occipital,  parietal  (2),  frontal,  temporal  (2),  sphenoid  and 
ethmoid;  those  of  the  face,  14  in  number,  nasal  (2),  lacrimal  (2),  vomer, 
malar  (2),  palate  (2),  turbinated  (2),  maxilla  or  upper  jaw  (2),  and 


THE  SKELETAL  OR  SUPPORTING  SYSTEM  45 

mandible  or  lower  jaw;  the  ear  bones,  three  pairs  in  number,  malleus  (2), 
incus  (2),  and  stapes  (2) ;  and  the  hyoid  at  the  base  of  the  tongue.  Most 
of  these  are  more  or  less  immovably  locked  together,  the  only  movable 
ones  being  the  mandible,  the  hyoid,  and  the  ear  bones. 

The  bones  of  the  spinal  column  are  31  in  number,  arranged  as  follows: 
7  cervical  or  neck  vertebra?;  12  dorsals  in  the  thoracic  region; 
7  lumbars  in  the  lumbar  region;  5  sacrals  in  the  pelvic  region;  and 
4  coccj/geals  forming  the  coccyx  or  rudimentary  tail.  The  first  two 
cer\'ical  vertebra?  are  specially  modified,  the  first  or  atlas  to  form 
the  connection  with  the  base  of  the  skull  and  the  second  or  axis  to 
form  a  special  kind  of  joint  with  the  first  to  allow  the  head  to  be  turned. 
The  dorsal  vertebrae  all  bear  ribs  attached  to  their  transverse  processes. 
The  lumbar  vertebrae  are  free  from  ribs  or  other  special  modification. 
They  are  the  largest  of  the  vertebrae  and  their  processes  are  well 
developed  for  the  attacJiment  of  muscles.  The  sacral  vertebrae  are 
fused  into  a  single  mass  to  afford  better  attachment  for  the  other  bones 
of  the  pelvis  to  which  the  legs  are  joined.  The  cocygeal  bones  are 
more  or  less  vestigial  vertebrae,  varying  somewhat  in  number,  but 
usually  four.  The  bones  of  the  spinal  column  are  all  capable  of 
being  moved  except  those  of  the  sacrum  and,  to  some  extent,  the 
coccyx. 

The  sternum  or  breast-bone  protects  the  main  organs  of  circulation 
and  respiration.  It  consists  of  three  parts  which  are  slightly  movable. 
To  the  upper  portion,  which  is  short,  are  attached  the  collar  bones 
and  the  first  pair  of  ribs.  The  body  of  the  sternum  has  the  cartilagin- 
ous portions  of  other  ribs  attached  to  it  down  to  and  including  the 
seventh  rib.  The  xiphisternum,  xiphoid  process,  or  ensiform  process, 
as  it  is  variously  called,  is  the  free  portion  of  the  sternum  projecting 
downward  over  the  stomach.  In  younger  years  it  is  cartilaginous,  but 
becomes  more  or  less  ossified  in  later  life. 

The  ribs  are  bony  arches,  12  in  number,  which  support  the  thoracic 
wall  and  protect  the  organs  of  circulation,  respiration,  and  to  some 
extent  the  upper  abdominal  organs.  The  first  seven  pairs,  called  true 
ribs,  are  attached  directly  to  the  sternum  by  continuations  of  hyaline 
cartilage.  The  next  three,  called  false  ribs,  are  attached  in  front, 
each  to  the  cartilage  of  the  next  rib  above.  The  last  two  pairs,  the 
floating  ribs,  are  not  attached  at  their  anterior  ends.  The  ribs  are  all 
attached  to  the  vertebrae  by  movable  joints,  so  that  in  respiration 
they  can  be  rotated  outward  and  upward,  and  the  costal  cartilages,  by 
which  they  are  attached  to  the  sternum,  permits  the  expansion  of  the 
anterior  thoracic  wall. 

In  the  appendicular  skeleton  the  framew^ork  of  the  upper  extremity 
consists  of  32  bones:  the  shoulder-blade  or  scapida,  the  collar-bone  or 
clavicle,  the  humerus  in  the  upper  arm,  the  radius  aufl  ulna  in  the  fore- 
arm, 8  carpal  bones  in  the  wrist,  5  metacarpals  in  the  hand,  and  14 
phalanges  in  the  fingers.  In  the  lower  extremity  the  bones  have  much 
the  same  arrangement.     On  either  side  is  one  large  irregular  shaped 


46  ANATOMY 

bone',  the  innoimnate,  to  form  the  sides  of  the  pelvis.  These  are  firmly 
united  behind  to  the  sacrum  and  to  each  other  in  front.  In  the  leg 
are  30  bones:  the  femur  or  thigh  bone,  the  pateUa  or  knee-cap,  the 
tibia  and  fihuhi  or  large  and  small  shin  bones,  7  tarsal  bones  in  the 
ankle,  one  of  which  is  the  heel-bone,  5  metatarsals  in  the  instep,  and  14 
phalanges  in  the  toes. 

Joints. — Bones  are  attached  to  each  other  by  joints  which  we  may 
classify'  in  the  following  manner: 

1.  Immovable  joints. 

2.  Slightly  movable  joints. 

3.  Freely  movable  joints. 

Of  the  immovable  joints  there  are  two  chief  types.  Sutures,  such 
as  are  found  between  the  bones  of  the  skull,  are  formed  by  the  inter- 
locking of  irregular  edges  of  adjoining  bones,  and  symphyses,  or  joints 
in  which  the  bones  are  closely  united  by  connective  tissue,  as  between 
the  innominate  bones  in  the  front  of  the  pelvis.  Both  sutures  and 
symphyses  often  become  completely  ossified  in  adult  life,  but  in 
younger  years  they  allow  the  parts  to  yield  slightly. 

Slightly  movable  joints  are  found  between  most  of  the  vertebrae  of 
the  spinal  column.  Here  pads  of  fibrocartilage,  the  intervertebral 
cartilages,  are  inserted  between  the  vertebrae  and  allow  the  column 
to  bend  in  any  direction  by  the  compression  of  the  cartilages. 

Movable  joints  are  those  in  which  the  bones  slip  or  rotate  past  each 
other  in  motion.  The  articular  surfaces  of  the  bones  forming  such 
joints  are  covered  with  hyaline  cartilage  and  between  the  bones  is 
found  a  closed  sac,  the  synovial  membrane,  which  secretes  a  slippery 
fluid  to  prevent  friction.     There  are  a  number  of  classes  of  these. 

1.  Gliding  joints,  in  which  the  articular  surfaces  are  nearly  flat  and 
the  bones  slip  past  each  other  slightly,  as  in  the  articular  processes  of 
the  vertebrae  and  the  bones  of  the  wrist  and  ankle. 

2.  Hinge  joints  are  those  which  permit  of  motion  in  only  one  plane 
as  in  a  hinge.  Examples  are  found  in  the  elbow,  knee,  and  between  the 
phalanges  of  the  fingers  and  toes. 

3.  Ball-and-socket  joints,  in  which  the  rounded  head  of  one  bone  is 
received  into  a  cup-shaped  cavity,  as  in  the  attachment  of  the  humerus 
at  the  shoulder  and  that  of  the  femur  to  the  pelvis.  This  i)ermits  of 
motion  in  any  plane. 

4.  Torsional  or  pivot  joints,  which  permit  one  bone  to  rotate  against 
another.  One  such  joint  occurs  between  the  first  and  second  cervical 
vertebne  to  permit  the  turning  of  the  head.  Another  is  found  in  the 
forearm  where  the  radius  twists  about  the  ulna  in  turning  the  hand 
over.  The  ulna  is  unable  to  twist  on  account  of  its  mode  of  attach- 
ment to  the  humerus,  and  the  hand  is  attached  to  the  radius  which 
twists  around   the   ulna. 

5.  Saddle  joints  are  formed  by  bones  whose  articular  surfaces  are 
concave  in  one  direction  and  convex  in  the  other.  Such  bones  fit 
together  like  a  man  in  a  saddle  and  allow  free  movement  in  any  direc- 


THE  MOTOR  OR  MUSCULAR  SYSTEM  47 

tion,  as  in  the  attachment  of  the  metacarpal  bone  of  tlie  thumb  to 
the  wrist. 

6.  Sliding  hinge. — There  is  only  one  pair  of  these  in  the  body,  at 
the  articulation  of  the  mandible  to  the  temporal  bone.  In  opening  the 
mouth  the  lower  jaw  not  only  acts  like  a  hinge,  but  the  head  or  con- 
dyle of  tlie  mandil)le  slides  forward  in  its  fossa  or  socket.  The  jaw 
can  be  shoved  forward,  backward,  and  sidewise. 

Levers. — The  levers  formed  by  the  movable  bones  of  the  body  are 
for  the  operation  of  the  joints  by  muscular  stress.  According  to  the 
principles  of  physics  they  fall  into  the  groups,  known  as  levers  of  the 
first,  second,  and  third  classes,  according  to  the  position  of  the  weight 
to  be  moved  and  the  point  of  application  of  the  power  which  moves  it. 

Arches. — The  skeleton  as  a  whole  consists  of  a  series  of  curves  and 
arches.  These  give  greater  elasticity  to  the  framework  and  help  to 
absorb  shock.  So  elaborate  is  this  arrangement  that  no  bone  is  with- 
out its  curved  surfaces  and  the  plan  is  carried  out  even  in  the  internal 
structure  of  the  bone. 

The  greater  curves  of  the  body  are  found  in  the  arches  of  the  feet 
which  are  of  the  greatest  importance  in  preventing  shock  in  walking, 
in  the  structure  of  the  pelvis  which  consists  of  a  series  of  arches,  and 
in  the  curves  of  the  spinal  column.  Any  shock  in  walking  which  might 
be  carried  upward  through  the  body  tends  to  be  shunted  ofl'  by  every 
one  of  these  larger  cur^'es  as  well  as  by  the  innumerable  smaller  ones, 
before  it  can  be  communicated  to  the  skull  and  the  brain.  Since  there 
are  twenty-two  of  the  intervertebral  pads  in  the  spinal  column,  in 
addition  to  the  curves,  it  is  evident  that  here  is  a  splendid  structure 
for  preventing  the  transmission  of  shock. 

THE   MOTOR   OR   MUSCULAR    SYSTEM. 

The  cells  of  the  body  which  are  specialized  for  contraction  make  up 
the  muscle  tissue.  The  function  of  these  cells  is  to  bring  about 
motion  by  shortening  their  length.  This  motion  may  be  concerned 
with  the  internal  affairs  of  the  body,  as  of  the  heart  in  circulation,  the 
intestinal  wall  in  peristalsis,  the  arterioles  in  controlling  the  flow  of 
blood,  etc.,  or  it  may  be  related  to  outside  matters,  as  in  the  move- 
ments of  the  eyeballs,  or  the  hands,  or  it  may  take  the  form  of  locomo- 
tion. As  these  movements  are  not  all  of  the  same  character,  some 
differentiation  of  the  contractile  tissues  is  to  be  expected.  In  the 
evolution  of  the  higher  animal  three  distinct  kinds  of  muscle  cells  have 
arisen  for  particular  uses.  -K^y!!:^ 

1.  Non-striated,  or  smooth  muscle,  not  under  control  of  the  will.  ^" 

2.  Cardiac  or  heart  muscle,  a  special  kind  found  only  in  the  heart 
and  also  in^'oluntary. 

3.  Cross-striated  or  striped  muscle,  often  known  as  voluntary 
muscle,  although  there  are  certain  of  these  muscles  such  as  the  dia- 
phragm and  intercostals,  used  in  breathing,  which  are  only  partially 


48 


ANATOMY 


under  the  control  of  the  will,  and  any  of  them,  under  certain  condi- 
tions, may  become  involuntary  in  action. 

The  smooth  nmscle  is  the  most  primitive  tj^pe  in  man  and  occurs 
commonly  in  lower  forms,  many  of  which  have  no  other  kind.  The 
cells  of  this  tissue  (Fig.  16)  are  small  and  spindle-shaped,  with  the 
nucleus  at  the  center,  without  cell  walls,  and  the  cytoplasm  is  faintly 
striped  in  a  lengthwise  direction,  a  characteristic  of  all  contractile 
tissues.  Cells  of  this  type  occur  in  the  intestinal  w^all,  in  the  ducts 
of  glands,  the  ureters,  the  blood  and  lymph  vessels,  the  iris  of  the  eye, 
the  skin,  etc.  The}'  are  very  slow  in  movement  in  comparison  with 
other  types  of  muscle  tissue.  There  are  no  tendons  in  connection  with 
this  sort  of  muscle,  since  it  usually  lies  in  the  walls  of  tubes,  the  sizes 
of  which  can  be  controlled  by  their  contraction. 
The  cells  are  intermingled  with  connective 
tissues. 

The  heart  or  cardiac  muscle  cells  differ  in 
being  block-like  in  form,  often  branched,  with 
a  central  nucleus  and  a  faint  cross-striation. 
They  also  have  no  cell  walls.  In  some  respects 
this  type  is  intermediate  between  the  other  two, 
yet  with  special  characters  of  its  own.  There 
are  some  tendons  in  connection  with  the  heart 
muscle,  particularly  the  chordoB  tendonce  which 
hold  the  valves  of  the  heart  in  place  during 
contraction.  The  heart  muscle  has  the  special 
property  of  automatic  action. 

Cross-striated  muscle  (Fig.  17)  is  highly  spe- 
cialized for  rapidity  of  contraction.  The  cells 
are  in  the  form  of  long  threads,  sometimes 
several  inches  in  length,  which  end  rather  bluntly. 
There  is  a  definite  cell  wall  known  as  the  sarco- 
lemma.  The  nuclei  are  very  numerous  and  are 
scattered  over  the  cytoplasm  immediately  under 
the  sarcolemma.  The  cytoplasm  is  much  more 
highly  differentiated  than  in  either  of  the  other 
kinds,  and  wc  find  not  only  the  lengthwise  striation  much  more 
definite,  but  there  is  also  a  very  definite  cross-banding  of  the  con- 
tractile substance.  This  character  seems  to  be  connected  with 
rapidity  of  action.  When  such  a  muscle  fiber  is  subjected  for  a 
time  to  the  action  of  alcohol,  it  tends  to  split  lengthwise  into  much 
more  delicate  threads  called  fihriUce.  When  treated  with  acid  the 
cell  substance  readily  breaks  crosswise,  forming  what  are  known  as 
Bowman's  disks. 

Contractile   tissues   are    very   widely   distributed   throughout   the 
body,  though  we  are  not  aware  of  the  action  of  many  of  them  when 
they  contract,  for  example,  those  in  the  skin,  bloodvessels,  intestirtal^ 
tract,  etc.     When  these  tissues  are  aggregated  into  definite  masses 


Fig.  16.— Fiber  cells 
of  plain  muscular  tis- 
sue (highly  magnified). 
(Kimber.) 


THE  MOTOR  OH  MUSCULAR  SYSTEM 


49 


they  are  referred  to  as  muscles.  But  muscular  tissue  is  not  always 
so  distributed;  in  fact  the  non-striated  type  is  generally  distributed 
in  the  form  of  sheets  or  layers,  such  as  those  we  find  in  the  walls  of 
the  bloodvessels  and  the  intestine  where  they  form  continuous  layers 
throughout  these  structures.  Even  in  the  heart,  though  there  are 
four  chambers,  the  muscles  which  govern  these  are  more  or  less 
continuous. 

The  great  mass  of  striated  muscle  tissue,  which  makes  up  so  large 
a  part  of  the  limbs  and  of  the  body  wall  and  which  is  usually  to  a 
greater  or  less  extent  untler  the  control  of  the  will,  is  characteristically 
divided  into  definite  muscles.     In  size  these  aggregations  range  from 


-'^OlOlliumminn- 
i3aR)innnmMiifHimnni«»-'~-,_<« 


'^^^m'&mmimmmm^ 


Fig.  17. — Wave  of  contraction  passing;  over  a  muscular  fiber  of  dyticu.s.  (Very  highly 
magnified.)  R,  R,  portions  of  the  fiber  at  rest;  C,  contracted  part;  /,  /,  intermediate 
condition.      (Schaefer.) 


the  almost  microscopic  muscles  which  move  the  tiny  ear  ossicles,  to 
the  large  muscles  of  the  limbs.  In  form  they  are  extremeh'  variable, 
in  adaptation  to  the  spaces  they  occupy  and  the  functions  they  per- 
form. As  a  rule  muscles  show  the  parts  known  as  the  belly,  origin,  and 
insertion.  The  belly  is  the  swollen  portion  such  as  is  seen  in  a  long 
muscle  like  the  biceps,  for  example,  though  it  is  usually  not  so  well 
marked  as  in  this  case.  At  each  end  such  a  muscle  tapers  off  into  the 
tendons  by  which  it  is  attached.  The  attachment  at  the  stationary 
end  is  known  as  the  origin  of  the  muscle,  and  that  upon  the  part  to  be 
moved  as  the  insertion. 

Such  muscles  are  usually  arranged  in  pairs  on  opposite  sides  of  the 
parts  the}^  are  concerned  in  moving.     Thus  the  biceps  lies  on  the  front 
4 


50  ANATOMY 

of  the  arm  and  the  triceps  on  the  back  of  it  and  they  are  inserted 
into  the  bones  of  the  forearm  which  they  move.  There  are  numerous 
departures  from  this  rule,  however,  and  certain  muscles  even  lie  free 
without  any  relation  to  the  skeleton,  such  as  the  diaphragm,  the  cheek 
muscles,  and  those  of  the  lips  and  eyelids.  Altogether  there  are 
about  five  hundred  separate  voluntary  muscles. 

If  we  examine  a  cross-section  of  a  muscle  we  will  find  on  the  outside 
a  connective-tissue  layer  forming  a  -binding  membrane  called  the 
fascia  or  perimysium.  Strands  of  similar  tissue  run  inward  from  this, 
di^•iding  the  muscle  into  large  portions  which  are  again  subdivided 
until  the  muscle  bundles,  consisting  of  a  number  of  muscle  fibers,  are 
formed. 

The  tendons  originate  among  the  connective  tissue  between  the 
muscle  cells. 

THE   NERVOUS   SYSTEM. 

This  system  has  the  function  of  correlating  the  activities  of  all  the 
other  systems  of  the  body,  as  well  as  of  relating  the  body  to  the  outside 
world  by  means  of  the  special  senses.  Therefore  we  naturally  expect 
to  find  nervous  tissues  widely  distributed  throughout  the  body. 

The  essential  structure  of  the  nervous  system  consists  of  the  nerve 
cells  or  neurons  (Fig.  18).  Each  neuron  is  made  up  of  a  cell  body  with 
at  least  two  processes  or  nerve  fibers  which  are  merely  extensions  of 
the  cell.  As  a  rule  one  of  these  nerve  fibers  is  longer  than  the  other 
and  is  known  as  an  axon.  The  cell  bodies  are  aggregated  into  masses 
called  ganglia.  The  "gray  matter"  of  the  brain  and  spinal  cord  con- 
sists of  large  numbers  of  these  nerve  cells,  while  the  "white  matter" 
consists  of  the  nerve  fibers.  The  fibers  are  often  collected  into  bundles 
for  convenience  of  distribution,  such  bundles  of  fibers  being  called  nerves. 

Xerve  cells  originate  impulses  and  also  receive  them  from  the 
sensory  endings  or  from  other  nerve  cells.  The  nerve  fibers  are  highly 
specialized  for  the  purpose  of  transmission  of  the  impulses.  The 
apparatus  is  often  compared  with  a  telegraph  system  in  which  the 
ganglia  represent  the  offices  where  messages  are  received  and  sent  out 
and  the  nerve  fibers  represent  the  wires  which  can  only  carry  the 
messages  sent  over  them. 

Neurons  communicate  with  each  other  by  having  their  processes 
in  close  contact,  though  they  do  not  form  a  continuous  network,  as 
was  formerly  supposed.  One  nerve  fiber  at  its  end  is  divided  into 
braric-hcs  called  terminal  arborizations,  and  these  are  closely  associated 
with  the  endings  of  branches  or  dendrites  of  other  cells.  An  impulse 
travels  in  only  one  direction  along  any  one  nerve  fiber  in  the  body,  and 
in  passing  from  one  cell  to  another  it  goes  outward  through  the  axon, 
over  the  terminal  arlxtrizations,  to  the  dendrites  of  the  other  cell  and 
on  to  the  cell  body.     This  process  is  not  reversible. 

Xerve  fibers  are  classified  according  to  the  direction  in  which  they 
carry  impulses. 


THE  NERVOUS  SYSTEM 


51 


1.  Afferent  fibers  are  those  which  conduct  inii)ulses  from  without 
toward  their  respective  cell  bodies.     A  fiber  carrying  impulses  from 


Fig.  18. — Scheme  of  central  motor  neuron.  (I.  type  of  Golgi.)  The  motor  cell  body, 
together  with  all  its  protoplasmic  processes,  its  axis-cylinder  process,  collaterals,  and 
end-ramifications,  represent  parts  of  a  single  cell  or  neuron,  a.h.,  axon-hillock  devoid 
of  Nissl  bodies,  and  showing  fibrillation;  c,  cytoplasm  showing  Nissl  bodies  and  lighter 
ground  substance;    n',  nucleolus.     (Barker.) 


the  skin  to  the  central  nervous  system  would  be  an  afferent  fiber.     The 
nerves  of  special  sense  all  belong  to  this  class. 


52 


ANATOMY 


2.  Efferent  fibers  are  those  which  conduct  impulses  away  from  the  cell 
bodies,  such  as  those  going  to  the  muscles  or  glands  to  govern  their 
action. 

3.  Commissural  fibers  are  those  which  run  from  one  nerve  cell  to 
another. 

A  nerve  usually  consists  of  both  afferent  and  efferent  axons  or  fibers, 
which  are  bound  together  in  one  bundle  for  convenience  in  distri- 


FiG.  19. — Diagram  illustrating  the  general  arrangement  of  the  eerebrospinal  system. 

(Kimber.) 


bution,  since  every  ])urt  of  the  body  requires  both  afferent  and  efferent 
coriiicftions.  \Vhcn  nerve  fibers  ])hss  out  to  any  distance  from  the 
ganglion  they  usually  have  a  special  coat  or  sheath  called  thevirdvllary 
sheath.  Such  nerve  fibers  are  said  to  be  medidlated  to  distinguish 
them  from  the  non-vied iillatcci  which  lack  the  sheath.  The  longest 
nerves  in  the  body  are  tho.se  which  go  to  the  extremities.     The  fibers 


THE  NERVOUS  SYSTEM 


53 


which  are  distributed  to  the  fingers  and  toes  have  their  cell  bodies  in 
the  spinal  cord. 
The  nervous  system  consists  of  two  chief  parts: 

1.  The  central  or  cerebrospinal  system. 

2.  The  sytit pathetic  system. 

The  Central  System. — ^The  central  system  is  made  up  of  the  gangli- 
onic or  cellular  masses  of  the  brain  and  spinal  cord  (Fig.  19),  together 
with  the  axons  or  fibers  belonging  to  these  cells.  The  principal  parts 
of  this  system  are  the  brain,  the  spinal  cord,  the  cranial  nerves  and  the 
spinal  nerves. 


r>  untul  lobe. 


Occipital 
lobe. 


Fig.  20. — Base  of  brain,  showing  superficial  origin  of  cranial  nerves.     (Little.) 


The  Brain  (Fig.  20).— The  brain  consists  essentially  of  great  masses 
of  cells  or  ganglia  (the  gray  matter)  with  their  commissural  fibers  and 
the  fibers  connected  with  the  cranial  nerves  and  spinal  cord.  It  is 
protected  within  the  skull  and  is  further  surrounded  by  three  con- 
nective-tissue membranes.  These  are  known  as  the  dura  mater, 
lining  the  bones  of  the  cranial  cavity;  the  pia  mater,  a  delicate  mem- 
brane closely  covering  the  surface  of  the  brain  and  richly  supplied 
with  bloodvessels;   and  the  arachnoid  which  is  between  the  other  two. 

The  largest  part  of  the  brain  is  the  cerebrum  or  forebrain,  which 


54  ANATOMY 

fills  the  whole  upper  part  of  the  skull.  Its  surface  is  deeply  and 
irregularly  convoluted  and  it  is  nearly  separated  into  right  and  left 
honispJicres  by  a  deep  furrow,  the  median  fissure.  At  the  bottom  of 
the  fissure,  however,  there  is  a  broad  band  of  commissural  fibers 
called  the  corpus  callosum. 

The  next  largest  portion  is  the  cerebellum  or  little  brain  situated 
behind  and  beneath  the  cerebrum.  It  is  only  about  one-seventh  as 
large  as  the  cerebrum.  Its  surface  is  regularly  convoluted  and  it  is 
divided  into  a  median  and  two  lateral  lobes.  A  broad  band  of  com- 
missural fibers  crosses  below  to  place  the  two  lateral  lobes  in  connec- 
tion.    This  band  is  known  as  the  pons  Varolii  (bridge  of  Varolus). 

The  medulla  oblongata  is  that  portion  of  the  brain  which  is  contin- 
uous with  the  spinal  cord.  It  is  situated  beneath  the  cerebellum 
immediately  behind  the  pons  Varolii. 

The  cavities  within  the  brain,  known  as  ventricles,  are  expansions 
of  the  minute  canal  which  runs  all  the  length  of  the  spinal  cord. 

There  are  twelve  pairs  of  nerves,  the  cranial  nerves,  connected  with 
the  brain.  Three  of  these  are  devoted  entirely  to  special  senses.  The 
first  pair,  the  olfactory  nerves,  have  to  do  with  the  sense  of  smell;  the 
second  pair  are  the  optic  nerves  or  nerves  of  sight;  and  the  eighth  pair 
are  the  auditory  nerves  or  nerves  of  hearing.  The  third,  fourth,  sixth, 
seventh,  eleventh,  and  twelfth  pairs  are  motor  nerves  distributed  to 
certain  muscles  of  the  head.  The  fifth,  ninth,  and  tenth  are  mixed. 
All  these  are  distributed  to  the  head,  except  the  tenth  (vagus  or  pneu- 
mogastric  nerve),  which  sends  fibers  to  the  esophagus,  heart,  and 
stomach  as  well.  The  cranial  nerves  emerge  from  the  skull  through 
openings  called  foramina. 

The  Spinal  Cord. — This  is  the  portion  of  the  central  nervous  system 
lodged  witliiu  the  spinal  column  and  it  is  in  direct  continuation  with 
the  brain.  It  is  not  as  long  as  the  column,  but  tapers  oflF  and  ceases 
at  the  le\'el  of  the  second  lumbar  vertebra.  The  same  three  protect- 
ing membranes  which  surround  the  brain  are  continued  down  around 
the  cord.  The  cord  is  deeply  grooved  in  front  and  behind  and  so  is 
nearly  separated  into  right  and  left  halves,  and  the  middle  is  pene- 
trated by  a  tiny  canal,  the  central  spinal  canal,  which  is  continuous 
with  the  ventricles  of  the  brain. 

The  spinal  nerves  number  31  pairs  arranged  as  follows: 
8  cervical  nerves  in  the  neck  region. 
12  dorsal  nerves,  corresponding  to  the  dorsal  vertebrae. 
5  lumbar  nerves,  corresponding  to  the  lumbar  vertebrae. 
5  sacral  nerves,  corresjjonding  to  the  sacral  vertebrae. 
1  coccygeal  nerve,  corresixdiding  to  the  first  coccygeal  vertebra. 

The  spinal  nerves  pass  out  through/om?/rirmoroj)enings  between  the 
vertebra,  but  the  lower  ones  run  for  some  distance  down  the  vertebral 
canal  before  they  emerge.  Each  spinal  nerve  has  two  roots,  a  dorsal 
anrl  a  \(Mitral,  which  merge  into  one  nerve  before  ])assing  out  of  the 
vertebral  canal.     The  dorsal  root  is  made  uj)  of  afferent  (sensory)  fibers 


THE  NERVOUS  SYSTEM 


55 


only  and  bears  a  gan<j:lion  through  which  every  incoming  sensory 
impulse  must  pass  before  it  enters  the  cord.  The  mntral  root  consists 
of  efferent  fibers  only.     After  the  nerves  emerge  from  the  column 


Carotid  pi< 


Pharyngeal  branches 


Cardiac  branches. 


Deep  cardiac  plexus 

Superficial  cardiac  plexus 


Solar  plexus- 


Aortic  plexus 


Hypogastric  plexus 


Sacral  ganglia. 


Ganglion  trnpar 


Fig.  21. — The  sympathetic  nerve  system.     (Gray.) 

they  often  send  off  connecting  branches  to  other  nerves  to  be  mingled 

with  them  in  their  distribution.     This  blending  is  known  as  a  plexus. 

The  gray  or  ganglionic  matter  of  the  cord  is  centralh'  located.     The 


56  -  ANATOMY 

rest  of  the  cord  is  made  up  of  nerve  fibers,  most  of  which  run  up  or 
down  the  cord. 

The  first  branch  of  a  spinal  nerve  communicates  with  a  ganglion  of 
the  sympathetic  system. 

The  Sympathetic  System. — This  consists  especiallj^  of  a  double 
chain  of  ganglia  (Fig.  21),  one  chain  on  either  side  of  the  spinal  column 
in  the  back  of  the  thoracic  and  abdominal  cavities.  In  addition  to 
these  ganglia  there  are  other  smaller  ones  in  the  heart,  intestine,  etc., 
which  are  connected  with  the  chains.  The  sympathetic  system  is  of 
the  greatest  importance  in  governing  the  so-called  vital  functions  of 
the  body.  Its  nerves  are  distributed  widely  over  the  body,  to  all 
the  organs  of  the  thorax  and  abdomen,  to  the  brain  and  eye,  and  to 
all  the  bloodvessels  of  the  body.  These  latter  nerves  are  of  two  classes, 
the  vasoconstrictor  and  vasodilator.  These  have  the  important  function 
of  regulating,  by  their  action  on  the  muscles,  the  size  of  the  blood- 
vessels and  consequently  the  distribution  of  the  blood. 

Nerve  Endings. — The  endings  by  which  the  neurons  communicate 
with  each  other  have  already  been  discussed.  The,  efferent  nerves, 
which  run  out  to  the  various  tissues,  have  different  endings  according 
to  the  sort  of  cells  they  stimulate.  In  the  voluntary  muscles  they 
form  end-plates  on  the  cells.  In  other  cases  they  may  end  as  fine 
fibrils,  etc.  The  afferent  nerves  which  have  their  sensory  endings 
in  the  skin  or  other  organs,  or  the  organs  of  special  sense,  end  in  a 
number  of  ways.  In  the  skin,  for  example,  are  found  delicate  fibrillar 
endings,  sensory  papilla?,  etc. 


CHAPTER   11. 
SPECIAL  ANATOIMY.i 

By  ROBERT  H.  W.  STRANG,  M.D.,  D.D.S. 

THE    SKXJLL. 

The  twenty-two  bones  that  enter  into  the  formation  of  the  osseous 
framework  of  the  head  are  united  by  immovable  joints,  the  lower 
jaw  excepted,  called  sutures.  These  form  a  strong  supporting  and 
protecting  structure  termed  the  skull.  This  may  be  conveniently 
studied  under  four  headings  (a)  the  cranium;  (b)  the  base;  (c)  the 
lateral  aspect;  (d)  the  anterior  aspect  or  face. 

The  Cranium. — The  cranium  comprises  that  portion  of  the  skull 
which  contains  the  brain.  It  is  formed  by  the  union  of  eight  bones. 
In  outline  it  is  somewhat  egg-shaped  and  presents  for  study  a  superior 
surface,  forming  the  vertex  of  the  skull,  and  an  inferior  surface. 

The  external  surface  of  the  vertex  is  convex  and  is  covered  in  the 
living  subject  by  the  tissues  that  form  the  scalp.  This  convexity  of 
surface  is  ideal  for  the  resisting  and  warding  off  of  blows.  This  surface 
is  traversed  by  three  sutures  arranged  in  the  form  of  the  letter  "H." 
The  anterior  cross  suture  which  is  situated  well  toward  the  top  of  the 
skull  is  called  the  coronal;  the  one  passing  from  this  to  the  posterior 
cross  suture  is  the  sagittal;  the  posterior  transverse  suture  is  the 
lamhdoid. 

The  internal  surface  of  the  vertex  is  concave  and  is  marked  with 
elevations  and  depressions  for  the  accommodation  of  the  irregular 
brain  surface.  Through  the  center,  running  anteroposteriorly,  is  a 
groove  in  which  lies  the  superior  longitudinal  sinus,  a  blood  channel 
performing  the  function  of  a  vein  and  carrying  part  of  the  return 
blood  from  the  brain.  To  the  margins  of  this  groove  are  attached 
some  of  the  supporting  membranes  of  the  brain. 

The  inferior  surface  of  the  crayiium  corresponds  to  the  cerebral 
surface  of  the  base  of  the  skull  (Fig.  22).  It  is  divided  by  two  trans- 
verse ridges  into  three  planes,  arranged  like  terraces  with  the  anterior 
one  on  the  highest  level.  These  planes  bear  the  name  of  fosscE  and 
are  called  according  to  their  position,  anterior,  middle  and  posterior^ 
Their  surfaces  are  more  or  less  irregularly  concave,  grooved  to  accom- 

1  Bibliography:  Gray's  Anatomy;  Cryer,  Internal  Anatomy  of  the  Face;  Deaver, 
Special  Anatomy  of  Head  and  Neck;  Swan,  Manual  of  Anatomy;  Noyes,  Dental  His- 
tology and  Embryology;  Chapter  on  Anatomy  of  the  Teeth,  by  C.  R.  Turner,  in  John- 
son's Operative  Dentistry. 


58 


SPECIAL  ANATOMY 


o'ruove/or  superior  sagittal  sinuS. 

Grooves  for  anterior  meu'nigeal  artery. 

Foramen  cxcum 

Ci'ista  gain 

tilitfor  nandl  nerve. 

Groove  for  nasal  nerve 

Anterior  ethmoidal  foramen. 

Orifices  for  olfactory  nerves. 

Posterior  ethmoidal  forame) 

Ethmoidal  spine. 


Olfactory  groove^ 

Optic  foramer 

Optic  groov:,. 

Olivary  process. 

.Anterior  clinoid  process. 

Middle  clinoid  process. 

Posterior  clinoid  process. 

Groove  for  6th  nerve. 

Foramen  lacerum  medium. 

Orifice  of  carotid  canal. 

Depression  for  Gasserian  ganglion. 


Meatus  auditorius  internus. 

Ftocculnr  foKsa. 

Superior  petrosal  groove. 

Foramen  lacerum  po.'tteritis 

Anterior  condylar  foramen: 

Aquxductus  veslihuli. 

Posterior  condylar  foramen. 


Mastoid  foramen 
Postei  ior  nieninge(d  grooves. 


Fig.  22. — Base  of  the  skull.      Inner  or  cerobrul  «urface.     (Gray.) 


THE  SKULL  59 

modate  bloodvessels  and  perforated  in  many  places  to  allow  these 
vessels  and  also  nerves  to  pass  in  and  out  of  the  cranium. 

Description  of  the  Fossae. — Anterior  Fossa. — The  points  of  interest 
in  this  fossa  are  (a)  the  prominent  bony  spine  in  the  median  line 
called  the  crista  galli  (cock's  crest) ;  (b)  near  the  front  end  of  this 
on  either  side,  slit-like  openings  for  the  passage  of  the  nasal  nerves 
into  the  nasal  cavity;  (c)  the  cribriform  plate  of  the  ethmoid  bone 
placed  on  a  somewhat  lower  level  than  the  rest  of  the  floor  of  the 
anterior  fossa  forming  what  is  known  as  the  olfactory  groove.  This 
groove  is  divided  anteroposteriorly  by  the  crista  galli,  accommodates 
the  olfactory  bulb  of  the  brain  and  has  its  floor  pierced  with  many 
openings  for  the  passage  of  the  olfactory  nerves  to  the  nasal  cavities; 
(d)  the  anterior  and  posterior  ethmoidal  foramina,  situated  at  the 
outer  edge  of  the  cribriform  plate,  the  former  at  about  the  middle 
and  the  latter  at  the  posterior  end  of  the  plate.  The  bone  forming 
the  floor  of  the  anterior  fossa  roofs  over  the  orbital  cavities. 

Middle  Fossa. — In  the  middle  fossa  are  seen  (a)  two  openings  that 
communicate  with  the  orbits.  The  smaller  of  these  is  the  optic  fora- 
men, transmitting  the  optic  nerve  and  ophthalmic  artery  to  the  eye; 
the  larger  one  is  the  sphenoidal  fissure  or  anterior  lacerated  foramen, 
for  the  passage  of  four  cranial  nerves,  a  sympathetic  nerve,  arteries 
and  veins  to  and  from  the  orbits;  (5)  in  the  center  of  the  fossa  a  bony 
formation  that  resembles  a  saddle  and  for  this  reason  is  called  the  sella 
turcica  (Turkish  saddle);  (c)  on  either  side  of  this,  four  openings. 
The  two  anterior  ones  are  of  particular  interest  because  through  them 
pass  the  divisions  of  the  fifth  cranial  nerve  that  go  to  the  upper  and 
lower  teeth.  The  anterior  opening  is  the  foramen  rotundum  and  it 
transmits  the  superior  maxillary  division  of  the  fifth  nerve.  Behind 
this  is  the  foramen  ovale  through  which  passes  the  sensory  and  motor 
portions  of  the  inferior  maxillary  division  of  the  same  nerve.  The 
largest  of  these  four  foramina  is  called  the  middle  lacerated  foramen. 
This  is  closed  in  the  living  subject  with  cartilage.  On  its  posterior 
wall,  however,  is  seen  (rf)  the  inner  opening  of  the  carotid  canal 
through  which  the  internal  carotid  artery  gains  entrance  to  the 
cranium. 

The  bone  at  the  posterior  aspect  of  the  middle  fossa  acts  as  the 
roof  for  the  middle  and  internal  divisions  of  the  ear  and  is  somewhat 
irregular  in  conformation  with  their  make-up. 

Posterior  Fossa. — The  surface  of  this  fossa  is  deeply  concave  and 
accommodates  the  cerebellum.  It  is  marked  with  (a)  grooves  for  the 
lateral  sinuses  carrying  return  blood  from  the  brain.  To  the  edges 
of  these  grooves  is  attached  the  membrane  supporting  the  cerebellum. 
{h)  The  foramen  magnum,  centrally  located,  through  which  passes  the 
spinal  cord;  (c)  the  anterior  condyloid  foramina  for  the  passage  of 
the  hypoglossal  nerves  to  the  tongue;  {d)  the  jugular  or  posterior 
lacerated  foramina  which  affords  a  means  of  exit  to  the  ninth,  tenth 
and  eleventh  cranial  nerves  as  well  as  the  lateral  sinuses;  {e)  the 


Anterior  palatine  fossa. 

Transmits  left  nasopalatine  nerve. 
Transmits  anterior  palatine  vessel. 
Transmits  right  nasopalatine  nerve 


Accessory  palatine  foramina. 

Posterior  nasal  spine. 

AZVGOS   UVUL/E. 

Hamular  process. 


Sphenoid  process  of  palate. 
Pterygopalatine  canal. 


TENSOR    TYMPANI. 

Pharyngeal  spine  for 

SUPERIOR    CONSTRICTOR. 

Situation  of  Eustachian  tube  and 
canal  for  tensor  tympani. 

TENSOR    PALATl. 

Canal  for  Jacobson's  nerve. 
Aguaeductus  cochleae. 
Foramen  lacenim  posterius. 
Canal  jor  Arnold's  nerve, 
A  uricular  fissure. 


Fig.  23. — Base  of  the  skull.     External  surface.     (Gray.) 


THE  SKULL  61 

internal  auditory  meati  for  the  i)assage  of  the  auditory  nerves  and 
arteries  and  the  facial  nerves. 

The  Base  of  the  Skull. — The  cerebral  surface  of  the  base  has  just  been 
described  under  the  heading  of  the  Inferior  Surface  of  the  Cranium. 
(Fig.  22.) 

The  external  nr  inferior  surface  of  the  base  (Fig.  23)  (the  mandible 
removed)  j)resents  the  following  points  for  study:  (a)  In  front  is  the 
hard  palate  bordered  by  the  teeth.  Behind  the  incisor  teeth  is  a  depres- 
sion in  the  ])alate  known  as  the  anterior  i^alatine  fossa.  In  the  floor 
of  this  fossa  are  four  foramina  for  the  passage  of  nerves  and  blood- 
vessels to  and  from  the  nose.  On  the  hard  palate  opposite  the  last 
molar  teeth  are  the  j^osterior  yalatinc  foramina  transmitting  arteries 
to  the  hard  palate.  (6)  Behind  the  hard  palate  are  seen  the  pos- 
terior openings  of  the  nasal  cavities  on  the  outer  sides  of  which  are 
the  two  pterygoid  processes  of  the  sphenoid  bone,  (c)  External  to 
these  processes  are  the  zygomatic  fossae  which  contain  three  of  the 
large  muscles  of  mastication,  the  inferior  maxillary  division  of  the 
fifth  nerve  and  the  internal  maxillary  artery.  These  fossse  communi- 
cate with  the  orbits  by  means  of  the  large  sphenomaxiUary  fissures. 
(f/)  Numerous  foramina  the  most  important  of  which  are:  ovale, 
external  opening  of  the  carotid  canal,  posterior  lacerated,  condyloid 
and  magnum,  (e)  Two  pairs  of  articulating  surfaces,  the  one  to 
receive  the  condyles  of  the  mandible  and  named  the  glenoid  fossce, 
the  other  to  articulate  with  the  first  vertebra.  (/)  The  styloid  and 
mastoid  processes  which  form  pronounced  landmarks  and  serve  for 
the  attachment  of  muscles. 

The  Lateral  Aspect  of  the  Skull. — The  following  landmarks  present 
themselves  for  study,  (a)  The  malar  bone  that  forms  the  promi- 
nence of  the  cheek.  (6)  The  zygoma  which  lies  very  superficially  and 
affords  attachment  to  the  masseter  muscle,  (c)  The  external  auditory 
meatus  and  (d)  the  styloid  and  mastoid  processes.  It  is  of  interest 
to  note  that  practically  all  of  the  bone  that  enters  into  the  formation 
of  the  side  of  the  skull  above  the  zygoma  is  covered  by  the  largest  of 
the  muscles  of  mastication,  /.  e.,  the  temporal. 

The  Anterior  Aspect  of  the  Skull  or  Face. — The  anterior  portion  of 
the  skull  is  termed  the  face.  Fourteen  bones  enter  into  its  make-up. 
Passing  from  above  downward  the  following  points  of  interest  are 
noted :  («)  The  supra-orbital  foramina  or  notches  through  which  pass 
an  artery  and  nerve  bearing  the  same  name,  (b)  The  orbits,  in  which 
well-protected  cavities  lie  the  eyes,  (c)  The  nasal  fossae,  (d)  The 
infra-orbital  foramina  which  transmit  the  infra-orbital  arteries  and  the 
end-branches  of  the  superior  maxillary  nerves,  (e)  The  prominent 
malar  bones.  (/)  The  teeth  of  the  upper  and  lower  jaws  supported 
by  their  alveolar  processes,  (g)  The  mental  foramina  through  each 
of  which  an  artery  and  ner^•e  of  the  same  name  emerge,  (h)  The 
mandible  or  lower  jaw. 


62  SPECIAL  ANATOMY 

The  Orbits. — These  are  irregular,  conical  cavities,  with  the  base 
toward  the  exterior  and  the  apex  inward.  The  outer  edge  of  the 
base  is  in  the  form  of  a  strong  bony  ridge  which  projects  a  little  beyond 
the  eye  and  thus  protects  it  from  injury.  Seven  bones  enter  into  the 
formation  of  the  walls  of  the  orbits.  On  the  superior  aspect  of  the 
outer  wall  near  the  base  is  a  depression  for  the  lachrymal  gland.  The 
orbit  is  in  communication  with  various  other  cavities  and  fossae  by 
means  of  the  following  openings:  (a)  The  optic  foramen  and  (6) 
sphenoidal  fissure  open  into  the  middle  fossa;  (c)  the  sphenomaxil- 
lary fissure  into  the  sphenomaxillary  and  zygomatic  fossae;  {d)  on 
the  inner  wall,  the  anterior  and  posterior  ethmoidal  foramina,  which 
transmit  vessels  of  the  same  names  and  the  former  also  the  nasal  nerve, 
lead  into  the  anterior  fossa;  and  (e)  the  nasal  duct  opens  into  the 
nose.  The  posterior  opening  of  the  infra-orbital  canal  is  seen  on  the 
floor  of  the  orbital  cavity. 

The  Nasal  Fossae. — These  are  large,  irregular  shaped  cavities  extend- 
ing from  the  floor  of  the  cranium  to  the  roof  of  the  mouth.  They  are 
separated  from  each  other  by  a  thin  partition  made  up  of  bones  and 
cartilage  and  called  the  nasal  septum. 

In  front  these  fossae  communicate  with  the  exterior  by  means  of 
two  large  openings  called  the  anterior  nares.  In  back  they  open  into 
the  pharynx  through  the  posterior  nares  or  choance. 

The  lateral  walls  are  very  irregular  and  are  divided  by  shelf-like 
bones  named  turbinates  (scroll-like)  into  three  or  more  sections 
called  meati.  The  turbinate  bones  are  normally  three  in  number  and 
according  to  their  position  receive  the  names  of  inferior,  middle  and 
superior. 

The  floor  of  the  nose  is  formed  by  the  same  bones  that  make  up 
the  hard  palate,  i.  e.,  the  palatal  process  of  the  superior  maxillary  and 
the  horizontal  process  of  the  palate  bones.  The  superior  surface  of 
these  processes  receives  the  name,  "floor  of  the  nose,"  while  the 
inferior  surface  is  called  the  "roof  of  the  mouth." 

The  nasal  fossae  are  in  communication  by  means  of  openings  and 
canals  with  the  following  cavities:  (a)  the  cranium,  {h)  the  orbits, 
(c)  the  pharynx,  id)  the  mouth,  {e)  three  sinuses,  i.  e.,  maxillary, 
frontal  and  sphenoidal,  and  (/)  three  sets  of  air  cells,  i.  e.,  anterior, 
middle  and  posterior  ethmoidal. 

According  to  function  the  nasal  fossae  are  divided  into  two  parts, 
the  olfactory  and  respiratory.  The  olfactory  area  is  in  the  upper 
portion  and  extends  flown  to  include  the  middle  turbinate  bones 
on  the  one  side  and  two-thirds  of  the  septum  on  the  other.  The 
respiratory  portion  takes  in  the  remainder  of  the  cavity. 

The  nose  is  lined  with  mucous  mem})rane  which  in  the  olfactory 
portion  is  non-ciliated  l)ut  contains  cells  that  are  specialized  to 
receive  the  sensations  productive  of  smell.  'J'hat  in  the  resi)iratory 
portion  is  much  thicker,  contains  large  plexuses  of  veins  and  its  cells 
are  of  the  ciliated  variety. 


THE  SKULL  63 

The  blood  fiiippJi/  to  the  nasal  cavity  comes  through  the  internal 
maxillary,  the  ophtliahnic  and  the  facial  arteries. 

The  nerve  supply  is  of  two  kinds:  (a)  that  of  special  sense  through 
the  first  cranial  or  olfactory  nerve  and  (6)  that  of  common  sensation 
through  the  fifth  cranial  or  trifacial  nerve. 

The  Bony  Sinuses  and  Air  Cells. — In  all  of  the  bones  of  the  skull 
that  have  any  great  thickness  we  hnd  cavities.  The  largest  of  these 
cavities  are  called  sinuses  while  the  smaller  ones  are  called  air  cells. 
Their  function  is  to  reduce  the  weight  of  the  bone  and  in  the  region 
of  the  mouth  and  nose  to  render  the  bone  more  resonant  for  the  pur- 
pose of  speech.  The  most  important  of  these  sinuses  and  air  cells 
are  the  following: 

Maxillary  or  Antra  of  Highmore. 
Sphenoidal. 
,       Frontal. 

Anterior,  iNIiddle  and  Posterior  Ethmoidal. 
Mastoid. 

The  Maxillary  Sinuses  or  Antra  of  Highmore. — These  are  two  in 
number,  situated  within  the  bodies  of  the  superior  maxillary  bones, 
external  to  the  nose  and  below  the  orbits.  In  shape  they  are  some- 
what pyramidal,  with  their  bases  directed  toward  the  nose  and  the 
apices  at  the  prominence  of  the  cheek.  They  open  into  the  nasal 
chamber  and  are  lined  with  mucous  membrane  which  is  directly  con- 
tinuous with  that  of  the  nose.  Often  the  roots  of  the  molar  and  bicus- 
pid teeth  form  elevations  on  the  floors  of  the  sinuses  and  when  diseased 
frequently  infect  the  mucous  membrane  with  most  serious  results. 

The  Sphenoidal  Sinus. — One  or  two  in  number  situated  within  the 
body  of  the  sphenoid  bone  at  the  posterior  aspect  of  the  roof  of  the  nose. 

The  Frontal  Sinuses. — These  are  two  fairly  large  cavities  within 
the  frontal  bone.  They  are  located  immediately  above  the  orbits 
and  their  position  is  marked  approximately  by  the  eyebrows.  They 
are  really  a  continuation  of  the  anterior  ethmoidal  air  cells  of  their 
respective  sides  and  open  by  way  of  these  cells  into  the  nasal  chamber. 
Congestion  of  these  sinuses  is  a  usual  sequence  in  a  so-called  "cold  in 
the  head,"  and  gives  rise  to  the  accompanying  headache  so  frequently 
noted  in  this  condition. 

The  Ethmoidal  Air  Cells. — There  are  three  sets  of  these  found  within 
the  lateral  masses  of  the  ethmoid  bone  and  named  according  to  their 
position,  anterior,  middle  and  posterior.  They  are  lined  with  mucous 
membrane  which  is  a  continuation  of  that  lining  the  nasal  passages 
into  which  each  set  of  cells  open.  These  cells  are  often  interconnected 
and  frequently  the  posterior  set  communicates  with  the  sphenoidal  sinus. 

The  orifices  of  the  canals  that  lead  from  the  nose  to  the  anterior 
ethmoidal  cells  are  intimately  associated  with  the  openings  into  the 
antra.  Thus  it  is  that  the  antrum,  the  anterior  ethmoidal  cells  and 
the  frontal  sinus  of  each  side  are  made  intercommunicating  and  their 
mucous  membrane  linings  practically  continuous  with  each   other. 


64  SPECIAL  ANATOMY 

These  anatomical  facts  make  it  very  possible  for  an  infection  arising 
within  one  cavity  to  travel  to  one  or  both  of  the  others.  Cases  are 
not  uncommon  in  which  an  abscess  on  the  root  of  an  upper  molar  or 
bicuspid  tooth  infects  the  mucous  membrane  of  the  antrum  and  the 
discharge  from  this  tissue  passing  into  the  nose  infects  the  lining 
membrane  of  the  canal  that  leads  to  the  anterior  ethmoidal  air  cells. 
The  infection  traveling  up  this  canal  will  eventually  involve  these 
cells  and  then  pass  on  to  the  frontal  sinus,  which,  as  has  been  before 
noted,  is  a  direct  continuation  of  the  anterior  ethmoidal  cells. 

The  mastoid  air  cells  or  antra  are  situated  within  the  mastoid  portion 
of  the  temporal  bones  and  will  be  mentioned  under  the  description  of 
the  ear. 

THE   EYES. 

These  are  the  organs  of  vision  and  consist  of  two  globular  bodies 
situated  within  the  orbits.  They  are  freely  movable  by  means  of  a 
ball-and-socket  joint  formed  between  the  eyeball  and  a  tough,  fibrous 
membrane  arranged  in  the  form  of  a  socket.  This  membrane  receives 
the  name  of  the  capsule  of  Tenon.  Movement  of  the  eyeball  is  per- 
formed through  the  agency  of  six  muscles  that  arise  from  the  bony 
wall  of  the  orbit  and  are  attached  to  the  ball  at  various  points. 

The  anterior  portion  of  the  eye  is  covered  with  a  modified  mucous 
membrane  which  is  reflected  onto  the  lids  and  lines  the  inner  side 
of  these.  This  membrane  is  called  the  conjunctiva  and  covers  that 
portion  of  the  eye  that  is  commonly  called  the  "white." 

The  eyeball  (Fig.  24)  is  made  up  of  three  coats  within  which  are 
three  refracting  media.    The  coats  are  named: 

1.  Outer  or  fibrous. 

2.  Middle  or  vascular. 

.3.  Inner  or  nervous.  • 

The  refracting  vicdia  are: 

1.  Aqueous  humor. 

2.  Crystalline  lens. 

3.  Vitreous  humor. 

The  Coats  of  the  Eye. — Fihrovs  Coat. — This  is  divided  into  two 
parts:  (a)  Cornea,  forming  the  anterior  sixth  of  the  sphere  and  (6) 
the  sclera,  forming  the  remainder,  (a)  The  Cornea.  This  tissue  is 
made  up  of  cells  that  will  transmit  the  raj's  of  light  and  so  may  be 
likened  to  a  window.  It  is  more  highly  convex  than  the  rest  of  the 
eye})all,  giving  this  portion  of  the  ball  a  bulging  appearance.  Its 
posterior  edge  is  continued  into  the  sclera,  (h)  The  Sclera.  This  is 
a  firm,  inelastic,  fibrous  membrane  forming  the  posterior  five-sixths 
of  the  eyeball. 

Va.scnlar  Coat. — This  is  di\ided  into  three  ])arts: 

The  iris. 

The  ciliary  body. 

The  choroid. 


THE  EYES 


65 


(a)  The  iris  may  })e  likened  unto  a  circular  curtain  attached  at  the 
periphery  and  perforated  in  the  center.  This  "hole"  in  the  center 
is  called  the  jmpil.  The  iris  contains  pigment  of  varying  tint  and 
is  the  tissue  that  gives  the  color  to  the  eye.  In  structure  it  con- 
sists for  the  most  i)art  of  muscular  fibers  of  two  kinds,  circular  and 
radiating.  When  the  circular  contract  the  pupil  becomes  smaller  and 
when  the  radiating  are  active  the  pupil  enlarges. 


VISUAL 
AXIS 


POSTERIOR   CHAMBER 
OF   EVE 


CILIARY 
PROCESS 


PARS     .ILIARIS 
RETINAE 


ORA   SERHATA 


PARS  OPT  IC 
RETIN/E 


MACULA    LUTEA 

AND 

FOVEA  CENTRALIS 


OPTIC 
EXCAVATION 


Fig.  24. — The  right  eye  in  horizontal  section.      (Toldt.) 


The  iris  is  suspended  in  a  cavity  formed  by  the  cornea  in  front  and 
the  lens  behind.  It  is  nearly  in  contact  with  the  latter  structure. 
This  cavity  is  known  as  the  anterior  chamber  of  the  eye  and  is  filled 
with  a  modified  lymph  called  the  aqueous  humor. 

(b)  The  ciliary  body  is  made  up  of  the  ciliary  processes  and  the 
ciliary  muscle.  The  ciliary  processes  are  composed  of  foldings,  as  it 
were,  of  the  tissues  making  up  the  middle  coat  and  are  continuous  at 
their  posterior  ends  with  the  choroid  and  at  their  anterior  ends  with 
the  suspensory  ligament  of  the  lens  and  the  iris.  They  vary  from  sixty 
to  eighty  in  number.  The  ciliary  muscle  is  arranged  in  the  form  of  a 
6 


66  SPECIAL  ANATOMY 

circular  band  of  iiRoluntary  muscle  fibers  lying  on  the  outer  surface 
of  the  middle  coat  of  the  eye  between  the  iris  and  the  choroid.  Its 
function  is  to  control  the  convexity  of  the  lens  so  that  the  rays  of  light 
may  be  properly  focussed.  The  ciliary  body  is  an  exceedingly  vascular 
area  and  consequently  is  very  liable  to  be  the  seat  of  an  infection, 
hence  it  has  been  designated  as  the  "danger  area"  of  the  eye. 

(c)  The  choroid  is  that  portion  of  the  middle  coat  that  lies  posterior 
to  the  ciliary  body.  It  is  made  up  of  areolar  tissue,  bloodvessels, 
and  considerable  pigment. 

Nervous  Coat. — This  is  commonly  called  the  retina.  It  is  continuous 
with  the  optic  nerve  behind  and  extends  forward  about  as  far  as  the 
ciliary  body  where  it  ends  in  a  jagged  margin.  It  may  be  called  the 
end-organ  of  the  optic  nerve  with  the  special  sense  of  vision  as  its 
function. 

The  fibers  of  the  optic  nerve  are  distributed  to  all  parts  of  this 
membrane  and  end  in  physiological  relationship  with  special  cells, 
the  rods  and  cones,  of  the  neuro-epithelium  lining  the  retina.  The 
rods  and  cones  receive  the  visual  impressions  and  transfer  them  to 
the  nerve  fibers. 

In  examining  the  retina  a  white  circular  area  is  noted  at  the  point 
of  entrance  of  the  optic  nerve.  This  is  called  the  optic  disc  and  is  the 
one  point  on  the  membrane  where  the  rays  of  light  will  make  no 
impression.  In  other  words,  it  is  a  blind  spot.  For  this  reason  it  is 
located  eccentrically  so  that  the  same  rays  of  light  will  not  he 
received  on  a  blind  spot  in  each  eye,  damaging  the  field  of  vision.  Its 
position  is  somewhat  to  the  inner  side  of  the  center.  Directly  in  the 
center  of  the  retina  is  the  area  where  the  most  acute  vision  is  to  be 
had.  This  is  called  the  macula  lutea  (yellow  spot)  because  of  its 
color. 

The  Interior  of  the  Eyeball. — The  interior  of  the  eyeball  is  divided 
into  two  compartments  by  the  lens.  These  are  known  as  the  anterior 
and  posterior  chambers  of  the  eye.  The  anterior  chamber  is  sub- 
flivided  by  the  iris  into  two  compartments  Avhich  communicate  with 
each  other  through  the  pupil. 

The  Refracting  Media. — The  Aqueous  Humor. — ^This  is  a  watery 
fluid  filling  the  anterior  chambers  of  the  eye.  It  is  derived  from  the 
vessels  within  the  ciliary  body  and  any  excess  is  carried  ofi'  through 
spaces  and  canals  that  empty  into  the  ciliary  veins. 

The  Crystalline  Lens. — This  is  a  biconvex,  circular  body  made  up  of 
transi)areiit  fibrous  tissue  the  component  parts  of  which  are  cemented 
together  with  a  transparent  cement  su})stance  and  the  entire  mass  of 
tissue  is  surrounded  by  a  capsule.  It  lies  in  a  depression  on  the  anterior 
surface  of  the  vitreous  body  and  is  held  in  position  by  the  suspensory 
ligament  of  the  lens.  The  function  of  the  lens  is  to  bring  the  rays  of 
light  to  a  proper  focus  upon  the  retina. 

The  Vitreous  Humor  or  Body. — In  contact  with  the  retina  and  filling 
the  interior  of  tiie  eyeball  behind  the  lens  is  the  vitreous  humor.     It 


THE  EARS  67 

is  composed  of  a  soft,  jelly-like  substance,  perfectly  transparent,  and 
made  up  of  semisolid  connective  tissue.  This  is  surrounded  by  a 
meml)rane  which  is  -thickened  anteriorly  to  form  the  suspensory 
ligament  of  the  lens  which  holds  the  lens  in  position  and  affords  attach- 
ment to  the  ciliary  processes.  The  anterior  surface  of  the  vitreous 
body  presents  a  cup-like  dei)ression  into  which  the  lens  fits. 

The  Lachrymal  Apparatus. — This  consists  of  (a)  the  lachrymal  or 
tear  ghuid  which  is  situated  in  a  depression  at  the  outer  angle  of  the 
orbit  at  its  upper  aspect  and  from  which  several  ducts  lead  and  open 
through  the  conjunctiva  of  the  upper  lid  just  before  this  is  reflected 
onto  the  eyeball;  (b)  the  lachrymal  sac,  placed  at  the  inner  angle  of 
the  orbit  and  gathering  in  the  tears  by  means  of  two  small  canals 
leading  from  the  inner  corner  of  each  lid;  and  (c)  the  nasal  duct,  a 
passage  that  leads  from  the  sac  to  the  inferior  meatus  of  the  nose 
and  discharges  its  contents  into  this  cavity, 

THE   EARS. 

The  organ  of  hearing  (Fig.  25)  is  divided  into  three  portions : 

1.  The  external  ear. 

2.  The  middle  ear. 

3.  The  internal  ear  or  labyrinth. 

The  External  Ear. — This  consists  of  the  cartilaginous  structure 
that  is  commonly  called  the  "ear"  and  the  external  portion  of  the 
auditory  canal.  The  latter,  known  as  the  external  auditory  canal,  is 
about  one  inch  in  length  and  runs  inward  and  somewhat  forward.  It 
is  separated  from  the  middle  ear  by  the  tympanic  membrane  or  drum. 
Its  external  opening  is  termed  the  external  auditory  meatus. 

The  Middle  Ear. — This  extends  from  the  drum  to  the  internal  ear. 
It  approximates  one-sixth  of  an  inch  in  length  and  is  nearly  one-half 
inch  in  its  verticle  diameter.  In  this  cavity  are  the  three  ear  bones 
or  ossicles,  as  they  are  called.  The  middle  ear  is  in  communication 
with  the  mastoid  antrum  through  a  small  opening  and  with  the  naso- 
pharynx via  the  Eustachian  tube. 

The  Tympanic  Membrane  or  Drum. — This  consists  of  an  oval  mem- 
brane, obliquely  attached  to  the  sides  of  the  auditory  canal,  the 
upper  portion  being  nearer  the  external  opening.  It  presents  a  con- 
cave surface  to  the  exterior.  Between  its  layers  is  bound  the  "handle" 
of  the  malleus,  one  of  the  ossicles. 

The  Ear  Ossicles. — These  are  three  in  number  and  are  named  from 
without  inward,  the  malleus  or  hammer,  the  incus  or  unvW  and  the 
stapes  or  stirrup,  (a)  The  malleus  is  bound  to  the  drum  by  means 
of  its  handle  while  its  so-called  head  articulates  with  the  body  of  the 
incus,  (b)  The  incus  is  shaped  very  much  like  a  bicuspid  tooth  in 
that  it  has  two  root-like  processes  projecting  from  a  body.  The  body 
articulates  with  the  malleus  and  the  longer  of  the  processes  with  the 
stapes,     (c)  The  stapes  on  the  one  hand  articulates  with  the  incus 


68 


SPECIAL   ANATOMY 


and  oil  the  other  fits  into  the  oval  window  located  on  the  wall  of  the 
internal  ear.  These  bones  are  held  in  position  by  ligaments  that 
are  attached  to  the  wall  of  the  middle  ear.  The  function  of  the  ear 
ossicles  is  to  transmit  and  magnify  the  sound  waves  received  by  the 
tympanic  membrane,  conveying  them  to  the  lymph  contained  within 
the  internal  ear. 

The  Mastoid  Antrum. — This  consists  of  a  moderately  large  cavity 
and  several  smaller  ones,  situated  within  the  mastoid  portion  of  the 
temporal  bone  just  behind  the  middle  ear  and  in  communication  with 
it.     These  air  cavities  are  often  the  seat  of  infection. 


Cartilage  of  auricula 
Attic 
Incus 

Malleus 

Tympanic  cavity 

Tensor  tympani 


Cartilaginous 

part  of  ext. 

acoustic  meatus 


Tympanic  membrane 


Bony  part  of 

ext.  acoustic 

rneatus 


Fig.  2.5. — External  and  middle  ear,  opened  from  the  front.     Riglit  side.      (Gray.) 

The  Eustachean  Tube. — This  canal  begins  at  the  anterior  end  of  the 
middle-car  ca\ity,  pas.ses  downward,  forward  and  somewhat  inward 
to  the  nasopharynx.  It  is  about  an  inch  and  a  half  in  length.  The 
finidion  of  the  pAistachian  tube  is  to  keep  the  air  within  the  middle 
ear  of  the  same  density  as  that  of  the  exterior.  This  prevents  any 
damage  to  the  drum  arising  from  inequality  of  air  j)ressure. 

The  Internal  Ear  or  Labyrinth  (i'ig.  2(')). — This  consists  of  three  parts: 

The  V('stii)iil('. 

I'he  cochlea. 

The  semicircular  canals. 


THE  EARS 


69 


Each  one  of  these  parts  is  made  up  of  bony  walls  enclosing  within 
them  a  membraneous  structure.  Separating  the  membraneous  por- 
tion from  the  bony  is  lymph  which  receives  the  name  of  perilymph, 
while  within  the  membraneous  structures  is  more  lymph,  termed 
endoli/nipli. 

Of  the  three  parts  of  the  internal  ear,  the  cochlea  is  placed  anteriorly 
and  the  semicircular  canals  posteriorly,  while  the  vestibule  lies  between 
them  and  serves  as  a  connecting  chamber. 

The  Vestibule. — In  the  external  wall  of  the  vestibule  is  the  oval 
window  into  which,  as  already  stated,  fits  the  base  of  the  stapes. 
The  vestibule  opens  into  the  cochlea  by  one  opening  and  into  the 
semicircular  canals  by  five  openings.  It  contains  two  membraneous, 
sac-like  structures,  the  utricle  and  the  saccule.  These  are  filled  with 
endolymph  and  are  connected  with  the  membranous  portions  of  the 


Fig.  26. — Right  osseous  labyrinth.     Lateral  view.     (Gray.) 


semicircular  canals  and  cochlea.  In  the  utricle  are  also  found  many 
minute  calcareous  bodies  called  otoliths.  These,  by  shifting  their 
positions  under  varying  conditions,  transmit  impulses  to  the  nerve 
filaments  in  the  mucous  membrane  of  the  utricle. 

The  Cochlea. — This  in  structure  resembles  a  snail's  shell  and  from 
the  exterior  is  somewhat  cone-shaped.  It  is  placed  with  the  apex  out- 
ward. In  its  base  are  found  numerous  openings  through  which  the 
branches  of  the  auditory  nerve  pass.  The  base  measures  about  two- 
fifths  of  an  inch  in  diameter  and  the  height  of  the  structure  is 
approximately  one-quarter  of  an  inch.  The  spiral  canal  within  the 
cochlea  makes  about  two  and  a  half  turns  around  the  central  axis. 
This  canal  is  divided  into  three  compartments  running  the  whole 
length  of  the  spirals.  In  the  median  compartment,  which  is  the 
membraneous  portion  of  the  cochlea,  is  the  organ  of  Corti,  the  name 
given  the  structure  which  receives  the  sound  waves  and  transmits 


70  SPECIAL  ANATOMY 

them  to  the  filaments  of  the  auditory  nerve  ending  within  the  mucous 
membrane  lining.    This  compartment  is  filled  with  endolymph. 

The  Semicircular  Canals. — These  are  thre^  in  number  and  come  oflP 
from  the  posterior  aspect  of  the  vestibule.  They  are  so  located  as  to 
be  at  right  angles  with  one  another.  Two  are  in  the  verticle  plane 
and  one  in  the  horizontal.  Within  these  are  the  membraneous  semi- 
circular canals,  external  to  which  is  the  perilymph  and  within  which 
is  the  endolymph.  They  are  lined  with  a  special  form  of  epithelivmi, 
the  cells  of  which  aie  in  intimate  relationship  with  the  end  filaments 
of  the  vestibular  branches  of  the  auditory  nerve.  These  canals 
undoubtedly  play  an  important  part  in  the  mechanism  concerned 
in  the  maintenance  of  the  equilibrium  of  the  body. 

Interconnection  of  the  Nerve  Supply  of  the  Ears  and  Teeth. — The  nerves 
to  the  ears  are  associated,  through  certain  of  the  cranial  ganglia,  with 
the  ner\'es  that  supply  the  teeth.  Hence  it  is  not  uncommon  to  have 
earache  accompanied  by  toothache  or  vice  versa.  At  times  earache 
may  be  the  only  symptom  of  a  dental  lesion. 

THE   MOUTH. 

The  mouth  may  be  defined  as  the  cavity  at  the  beginning  of  the 
alimentary  canal.  It  is  bounded  in  fro7it  by  the  lips;  laterally  by  the 
cheeks;  above  by  the  hard  and  soft  palates;  and  below  by  the  mylo- 
hyoid muscle  which  forms  its  floor.  It  contains  the  teeth  and  the 
tongue.  Anteriorly  the  mouth  opens  to  the  exterior  through  the 
lips  and  posteriorly  into  the  pharynx  through  the  fauces.  The 
mouth  cavity  is  divided  into  two  portions:  (a)  the  vestibule,  which 
lies  between  the  lips,  cheeks  and  teeth,  and  (b)  the  mouth  proper  or 
oral  cavity,  internal  to  the  teeth.  It  is  lined  with  mucous  membrane 
of  the  stratified  squamous  variety.  This  membrane  contains  many 
mucous  glands  which  pour  their  contents  into  the  mouth. 

The  bony  framework  of  the  mouth  is  formed  by  (a)  the  superior 
maxillary  bones,  (6)  the  palate  bones,  and  (c)  the  inferior  maxillary 
bone  or  mandible. 

The  Superior  Maxillary  Bones  (Fig.  27). — These  are  two  in  number 
and  form  the  bulk  of  bone  below  the  forehead  exclusive  of  the  promi- 
nences of  the  cheeks.  Each  superior  maxilla  consists  of  a  body  and 
four  processes. 

The  Body. — On  the  anterior  surface  is  seen,  from  above  downward: 
(a)  a  portion  of  the  orbital  margin;    (6)  the  infra-orbital  foramen; 

(c)  incisive  fossa,  a  depression  above  the  roots  of  the  incisor  teeth; 

(d)  the  canine  fossa,  a  depression  behind  the  prominent  root  of  the 
cusj)id  tooth,  and  (e)  the  ridges  of  bone  overlying  the  roots  of  the 
incisor  and  cuspid  teeth;  (/)  in  the  median  line  a  sharp  process  of 
bone  called  the  nasal  spine. 

The  superior  surface  of  the  body  forms  a  ])()rtion  of  the  floor  of 
the  orbit.     It  presents  the  inner  opening  of  the  infra-orbital  canal. 


THE  MOUTH 


71 


From  this  canal  are  ^iven  off  branch  canals  which  convey  the  blood- 
vessels and  nerves  to  the  anterior  teeth  and  bicuspids. 

The  posterior  surface  forms  part  of  the  zygomatic  fossa  and  pre- 
sents the  openings  of  canals  that  take  the  bloodvessels  and  nerves 
to  the  molar  teeth. 

The  iniernal  or  nasal  surface  forms  a  portion  of  the  outer  wall  of 
the  nasal  cavity.  It  presents  the  opening  that  leads  into  the  maxil- 
lary sinus  or  antrum  of  Highmore.  This  large  air  cavity  is  situated 
within  the  body  of  the  superior  maxillary  bone  and  has  been  described 
under  the  heading  of  Sinuses. 

Outer  Surface. 


TENDO    crcULi 


Incib'iie  fossa. 


Posterior  dental 
canals. 


Mujcillary  tuberosity 


''^^-  a^ 


ine.     Bicuspids. 


MoW^*" 


Fig.  27. — Left  maxilla.     Outer  surface. 


The  Four  Processes: 

1.  Nasal. 

2.  Malar. 

3.  Palate. 

4.  Alveolar. 

The  uasal  process  is  situated  between  the  nose  and  the  orbit,  pro- 
jecting upward  from  the  body  of  the  bone. 

The  malar  process  manifests  itself  on  the  outer  surface  of  the  bone 
and  articulates  with  the  malar  bone. 

The  palate  process  projects  horizontally  from  the  inner  surface  of 
the  body,  articulates  with  the  corresponding  process  of  the  superior 


il 


SPECIAL  ANATOMY 


maxillary  bone  of  the  opposite  side  and  thus  forms  with  its  supe- 
rior surface  the  anterior  portion  of  the  floor  of  the  nose  and 
with  its  inferior  surface,  the  corresponding  portion  of  the  roof  of 
the  mouth. 

The  alveolar  process  is  built  up  on  the  lower,  outer  border  of  the 
body  for  the  purpose  of  supporting  the  teeth,  the  roots  of  which  are 
found  within  its  substance. 

The  Palate  Bones. — These  are  two  in  number.  In  form  they  may  be 
likened  to  the  letter  "L."  Their  upright  portion,  called  the  verticle 
plate,  helps  to  form  the  outer  wall  of  the  nasal  cavity.  The  bone 
corresponding  to  the  base  of  the  "L"  is  called  the  horizontal  plate  and 
articulates  anteriorly  with  the  palate  process  of  the  superior  maxilla, 
thus  aiding  in  the  formation  of  the  floor  of  the  nose  and  roof  of  the 
mouth.  Posteriorly  the  horizontal  plate  ends  in  a  free  border  to  which 
is  attached  the  soft  palate. 


GENIOHYOGLOSSUS 


GENIOHYOIDEU8 


Mylohyoid  ridge 


Body. 


Fig.  28. — The  iiiaiulihle.     Inner  surface.     Side  v^iew. 


The  Inferior  Maxillary  Bone  or  Mandible  (1^'ig.  2<S). — In  form  this 
bone  resemljles  a  horseshoe  and  is  composed  of  a  hody  and  two  rami. 
The  latter  arise  from  the  posterior  ends  of  the  body.  The  angle 
formed  between  the  rami  and  the  body  varies  in  degree  according  to 
race,  ty[H'  and  ago.  "^I'lic  niMiidiblc  is  the  oiiIn'  ])()ne  in  the  skull  that  is 
movable. 

The  Body. — The  external  .surface  is  usually  concave  from  above 
downward,  and  ends  below  in  a  thick  ridge.  In  the  median  line  in 
front  is  another  thick  ridge  jjlaced  at  right  angles  to  the  border.    This 


THE  MOUTH  73 

receives  the  name  of  symphysis  menti.  Below,  this  fuses  with  the 
lower  border  of  the  bone  to  form  the  prominence  of  the  chin. 

In  the  region  of  the  first  and  second  bicuspid  teeth  and  about 
half-way  between  the  upper  and  lower  borders  of  the  bone  are  seen 
the  inentdl  forcunina,  one  on  either  side.  These  are  the  anterior  open- 
ings of  the  mandibular  canals  and  transmit  the  mental  vessels  and 
nerves.  The  alveolar  process  is  built  on  the  superior  border  of  the 
body  and  serves  to  maintain  the  lower  teeth  in  position. 

The  internal  surface  (Fig.  28)  presents  in  the  median  line  four 
tubercles  for  the  attachment  of  muscles.  Passing  back  from  these  along 
the  body  of  the  bone  and  half-way  between  its  borders  is  a  ridge  called 
the  mylohyoid  ridge.  This  serves  for  the  attachment  of  the  muscle 
of  the  same  name  which  forms  the  floor  of  the  mouth.  Above  this 
ridge  just  to  either  side  of  the  median  line  are  two  depressions  called 
the  sublingual  fossoe  and  resting  in  these  lie  the  sublingual  glands. 
Below  this  ridge  in  the  region  of  the  bicuspid  and  molar  teeth  on  either 
side,  are  two  other  depressions  that  receive  the  submaxillary  glands. 
The  sublingual  and  submaxillary  glands  pour  their  secretion  into  the 
mouth  through  a  common  duct,  Wharton's,  the  opening  of  which  is 
on  either  side  of  the  frenum  of  the  tongue. 

The  Rami. — The  external  surface  of  each  ramus  serves  for  the 
attachment  of  one  of  the  muscles  of  mastication,  the  masseter.  The 
posterior  border  terminates  below  in  what  is  commonly  called  the  angle 
of  the  jaw.  The  internal  surface  serves  as  a  place  of  attachment  for 
certain  of  the  muscles  of  mastication,  ?.  e.,  the  internal  pterygoid  and 
the  temporal.  This  surface  presents  about  at  its  midpoint  an  opening, 
the  inferior  dental  foramen,  which  leads  into  the  canal  of  the  same 
name.  It  transmits  the  inferior  dental  artery  and  nerve  which  furnish 
the  blood  and  nerve  supply  to  the  lower  teeth. 

The  superior  border  of  each  ramus  presents  two  prominences 
between  which  is  a  well-marked  notch.  The  anterior  prominence  is 
called  the  coronoid  process  and  serves  for  the  attachment  of  the 
temporal  muscle.  The  posterior  prominence  is  surmounted  with  an 
articular  cartilage,  receives  the  name  of  the  condyle,  and  enters  into 
the  formation  of  the  temporomaxillary  articulation. 

The  Temporomaxillary  Articulation. — This  is  a  sliding  hinge  joint 
and  is  formed  by  the  glenoid  fossa  on  the  base  of  the  skull  and  the 
condyle  of  the  mandible.  The  glenoid  fossa  is  somewhat  cup-shaped 
and  is  limited  anteriorly  by  a  ridge,  the  eminentia  articnlaris.  This 
aids  the  ligaments  of  the  joint  in  restricting  the  forward  slide  of  the 
mandible.  The  articulating  surface  of  the  condyle  is  oblong  with  the 
long  diameter  in  the  transverse  plane. 

The  Muscles  Active  in  Moving  the  Mandible. — These  may  be  divided 
into  two  sets:  (a)  the  so-called  "  muscles  of  mastication"  which  bring 
the  lower  teeth  in  contact  with  the  upper  in  the  process  of  chewing 
by  raising  the  mandible  and  {h)  the  depressor  muscles  or  those  which 
pull  the  mandible  downward  as  in  opening  the  mouth. 


74  SPECIAL  ANATOMY 

(a)  The  muscles  of  mastication  are  five  in  number,  i.  e. : 

Temporal. 
INIasseter. 
Buccinator. 
Internal  pterygoid. 
External  pterygoid. 

(b)  The  depressor  muscles  are  also  five  in  number. 

The  Lips  and  the  Cheeks. — These  structures  are  made  up  of  muscles 
and  fibro-elastic  tissue.  They  are  covered  on  the  external  surface 
with  skin  and  on  their  internal  or  oral  surface  with  mucous  mem- 
brane. These  two  coverings  unite  at  the  outer  border  of  the  lips. 
The  mucous  membrane  contains  many  mucous  glands  which  pour 
their  secretion  into  the  mouth  cavity.  In  the  center  of  the  upper  lip 
and  sometimes  of  the  lower  a  fold  of  mucous  membrane  is  reflected 
onto  the  alveolar  process.    This  is  called  the  frenum. 

On  the  inside  of  the  cheek  about  opposite  the  upper  second  molar 
tooth  is  seen  a  small  papilla  which  marks  the  opening  of  the  duct 
leading  from  the  parotid  gland. 

The  Hard  Palate. — The  hard  palate  is  formed  by  the  palate  processes 
of  the  superior  maxillary  bones  and  the  horizontal  processes  of  the 
palate  bones.  Posteriorly  it  ends  in  a  free  border  to  which  the  soft 
palate  is  attached.  It  is  covered  w^ith  mucous  membrane  the  surface 
of  which  anteriorly  is  thrown  into  folds,  called  rugcB. 

The  Soft  Palate. — ^This  structure  is  attached  to  the  posterior  border 
of  the  hard  palate  and  is  formed  by  five  different  muscles.  These 
are  in  turn  covered  with  mucous  membrane.  The  function  of  this 
structure  is  to  shut  off  the  nasal  passage  from  the  mouth  during  the 
act  of  swallowing. 

The  Tongue. — The  tongue  is  a  muscular  organ  composed  of  a  root, 
a  body  and  an  anterior  free  extremity  or  tijJ.  It  is  made  up  of  five 
muscles  and  is  covered  with  mucous  membrane.  The  under  sur- 
face is  attached  to  the  floor  of  the  mouth  by  a  fold  of  this  membrane 
called  the  frenum.  The  base  of  the  tongue  is  attached  to  the  hyoid 
bone  and  to  the  muscles  of  the  pharynx. 

On  the  surface  of  the  tongue  are  seen  three  varieties  of  papillae. 
These  are  composed  of  a  connective-tissue  core  developed  in  the 
corium  (tissue  under  the  epithelium)  and  covered  with  epithelium. 
The  most  important  of  these  papilUe  are  situated  on  the  back  part 
of  the  tongue,  are  arranged  in  the  form  of  a  "V"  with  the  point  back- 
ward, are  eight  to  twelve  in  number  and  are  called  clrcumvallate  pap- 
illoB.  At  the  base  of  these  papilla?  are  located  the  taste  buds,  specialized 
bodies  in  which  filaments  of  the  glossopharyngeal  nerve  end  and 
through  which  media  the  sense  of  taste  is  active. 

On  the  base  of  the  tongue,  behind  the  clrcumvallate  "papilla',  is 
found  considerable  lymphoid  tissue.  This  is  given  the  name  of  the 
lingual  torufil. 

The  nerve  supply  of  the  tongue  is  interesting  in  that  it  is  derived 


THE  MOUTH 


75 


from  three  different  sources,  (a)  The  nerve  of  special  sense  has  been 
mentioned  above  as  the  glossopharyngeal,  {h)  The  nerve  of  com- 
mon sensation  is  the  fifth  cranial  or  trifacial  and  (c)  the  motor  nerve 
to  the  muscles  of  this  organ  is  the  hypoglossal  or  twelfth  cranial. 

The  Nerve  and  Blood  Supply  of  the  Dental  Tissues. — The  nerve 
supply  to  the  structures  entering  into  the  formation  of  and  associated 
with  the  oral  cavity  is  through  the  trifacial  or  fifth  cranial  nerves  and 
the  facial  or  seventh  cranial  nerves.  Their  blood  supply  is  brought 
by  the  internal  maxillary  artery,  a  branch  of  the  external  carotid 
arterv. 


Seiiso) y  loot 
Motoi  loot 


Au)  xculo-tempoi 
net  ve 


Fig.  29. — Distribution  of  the  second  and  third  divisions  of  the  trigeminal  nerve. 

(Gray.) 


The  Trifacial  or  Fifth  Cranial  Nerve  (Fig.  29).— This  is  the  great 
sensory  nerve  of  the  head  and  face.  It  also  contains  a  few  motor 
fibers.  It  leaves  the  pons  Varolii  (a  portion  of  the  spinal  cord  just 
below  the  brain)  in  the  form  of  two  roots,  an  anterior  motor  and  a 
posterior  sensory.  The  latter  root  enters  a  large  ganglion,  the  Gas- 
serian,  situated  on  the  floor  of  the  middle  fossa  of  the  skull  just  behind 


76  SPECIAL  ANATOMY 

the  foramen  ovale.     From  this  ganghon  three  large  trunks  are  given 
off  as  follows: 

The  ophthalmic  or  first  division. 

The  superior  maxillary  or  second  division. 

The  inferior  maxillary  or  third  division. 
The    ophthalmic    division    passes    forward   and    enters   the    orbit 
through    the   sphenoidal   fissure  supplying  the  various  structures  in 
this  cavity,  the  nasal  cavity  and  the  upper  part  of  the  face,  with 
sensation. 

II.  The  superior  maxiUarij  division  lea\-es  the  cranium  through 
the  foramen  rotundum  entering  the  sphenomaxillary  fossa.  From  this 
fossa  it  gains  entrance  to  the  orbit  via  the  sphenomaxillary  fissure. 
It  passes  along  the  floor  of  the  orbit  to  the  infra-orbital  canal  which 
it  enters  and  then  emerges  from  the  canal  through  the  infra-orbital 
foramen  to  supply  the  tissues  in  the  region  of  this  opening.  Just 
before  this  division  enters  the  orbit  it  gives  oft'  branches  that  supply 
the  upper  molar  teeth.  These  reach  the  teeth  by  passing  through 
bony  canals,  the  entrance  to  which  are  found  on  the  posterior  surface 
of  the  superior  maxillary  bones.  AYhile  in  the  infra-orbital  canal 
branches  are  given  oft"  that  supply  the  upper  bicuspid,  cuspid  and 
incisor  teeth. 

There  are  no  motor  fibers  found  in  either  the  ophthalmic  or  superior 
maxillary  divisions  of  this  nerve.  Their  function  is  purely  a  sensory 
one,  that  of  touch  and  pain,  to  those  structures  to  which  they  are  dis- 
tributed. 

The  inferior  maxillary  division  emerges  from  the  cranium  through 
the  foramen  ovale.  Accompanying  it  through  this  opening  is  the  motor 
root  of  the  nerve  which  joins  the  sensory  division  just  outside  the 
cranium.  This  combined  trunk  is  now  located  in  the  zygomatic  fossa 
and  almost  immediately  is  found  to  divide  again.  One  of  these  divi- 
sions contains  nearly  all  of  the  motor  fibers  and  is  distributed  to  the 
muscles  of  mastication,  excluding  the  buccinator.  The  other,  containing 
V)ut  a  few  mf)tor  fibers  and  made  up  mostly  of  sensory  ones,  is  the  larger 
of  the  two  and  divides  into  three  branches,  i.  e.,  (a)  the  auriculotem- 
poral, w^hich  supplies  the  tissues -about  the  ear,  the  temporomandib- 
ular articulation  and  sends  communicating  branches  to  the  facial 
(seventh  cranial)  nerve;  {h)  the  lingual  which,  as  previously  stated, 
supplies  common  sensation  to  the  tongue;  and  (c)  the  inferior  dental 
nerve.  This  last  branch  enters  the  mandibular  canal  in  the  body  of 
the  inferior  maxillary  bone,  traverses  its  entire  length  and  emerges 
through  the  mental  foramen  as  the  mental  nerve  to  supply  sensation 
to  the  surrounding  tissues.  AVhile  in  the  mandil)ular  canal  minute 
branches  are  given  oft'  to  the  various  lower  teeth. 

Just  as  the  inferior  dental  nerve  is  about  to  enter  the  mandibular 
canal  it  gives  oft'  quite  a  large  branch,  the  mylohyoid  nerve.  This 
contains  motor  fibers  and  ])asses  flf)\\nward  to  supply  the  mylohyoid 
anfl  digastric  muscles. 


THE  MOUTH  77 

The  Facial  or  Seventh  Cranial  Nerve. — This  is  the  great  motor  nerve 
of  the  head  and  t'aee.  It  supplies  the  museles  of  expression,  certain 
of  the  ear  museles,  one  of  the  museles  of  mastication,  the  buccinator, 
and  sends  communicatinfj  })ranches  to  two  important  cranial  o;an<,dia. 

The  facial  nerve  emerges  from  the  pons  \'arolii  and  enters  the 
internal  auditory  meatus  accompanying  the  auditory  nerve  and  artery. 
It  soon  leaves  the  auditor^'  canal  and  enters  another  bony  canal  known 
as  the  aqueductus  Fallopii  and  comes  out  on  the  exterior  of  the  skull 
through  the  stylomastoid  foramen.  It  then  enters  the  substance  of 
the  ])arotid  gland  and  breaks  up  within  this  structure  into  a  large 
terminal  arborization  known  as  the  pes  anserinus  (duck's  foot). 

Within  the  aqueductus  Fallopii  several  branches  are  given  off, 
two  of  which  go  to  cranial  ganglia.  After  leaving  the  stylomastoid 
foramen  branches  are  given  off  to  muscles  attached  to  the  temporal 
bone  near  the  styloid  process  and  about  the  external  auditory  meatus. 
The  branches  forming  the  terminal  arborization  supply  the  muscles 
of  expression  situated  about  the  eyes,  nose,  and  the  upper  and  lower 
lips.    One  of  these  branches  also  supplies  the  buccinator  muscle. 

The  Internal  Maxillary  Artery. — This  is  one  of  the  terminal  branches 
of  the  external  carotid  artery  and  arises  from  that  vessel  at  a  point 
just  below  the  condyle  of  the  mandible.  It  embeds  itself  deeply  in 
the  substance  of  the  parotid  gland,  passes  internal  to  the  ramus  of 
the  jaw,  through  the  zygomatic  fossa  to  the  sphenomaxillary  fossa. 
Here  it  breaks  up  into  its  terminal  branches.  One  of  these,  the  infra- 
orbital, is  really  a  continuation  of  the  main  trunk  and  enters  the  orbit 
through  the  sphenomaxillary  fissure,  passes  forward  on  the  floor  of 
the  orbit  in  company  with  the  superior  maxillary  division  of  the  fifth 
nerve,  enters  the  infra-orbital  canal  and  emerges  onto  the  face  through 
the  infra-orbital  foramen.  While  in  the  infra-orbital  canal  it  gives  off 
branches  that  supply  the  upper  bicuspid,  cuspid  and  incisor  teeth. 

Important  Branches  of  the  Internal  Maxillary  Artery. — Soon  after 
its  origin  from  the  external  carotid,  the  internal  maxillary  artery 
gives  off  (a)  the  middle  meningeal  artery,  that  passes  upward  and 
enters  the  cranium,  therein  to  supply  the  various  bones  entering  into 
the  formation  of  this  structure  and  (6)  the  mandibular  or  inferior 
dental  artery,  that  passes  downward  in  company  with  the  inferior 
maxillary  division  of  the  fifth  nerve  and  enters  the  mandibular  canal. 
It  gives  off  branches  to  the  lower  teeth  as  it  passes  through  the 
canal  and  then  emerges  onto  the  chin  as  the  mental  artery  through 
the  foramen  of  the  same  name,  (c)  Branches  to  the  muscles  in  the 
maxillary  region  given  off  as  the  artery  traverses  the  zygomatic  fossa. 
(d)  In  the  sphenomaxillary  fossa  small  branches  that  enter  the  canals 
in  the  posterior  portion  of  the  superior  maxillary  bones  and  supply 
the  u])per  molar  teeth,  (e)  The  infra-orbital  artery  which  has  been 
described  in  the  preceding  paragraph. 

The  Salivary  Glands. — There  are  three  pairs  of  these  glandular  struc- 
tures, /.  e.:    (a)  parotid;  (h)  the  submaxillary;  and  (c)  the  sublingual. 


78  SPECIAL  ANATOMY 

The  parotid  (near  the  ear)  glands,  one  on  either  side,  are  situated 
below  and  in  front  of  the  ears  and  extend  from  the  zygoma,  above, 
to  the  angle  of  the  jaw,  below.  Their  ducts,  called  Steno's  or  Sten- 
son's,  open  into  the  mouth  at  points  about  opposite  the  upper  second 
molar  teeth. 

The  svbmaxillary  glands  are  situated  below  the  floor  of  the  mouth, 
in  contact  with  the  inner  surface  of  the  mandible  in  the  region  of  the 
bicuspid  and  molar  teeth.  The  ducts  from  these  glands  join  with  the 
ducts  from  the  sublingual  glands  and  make  their  entrance  into  the 
mouth  on  either  side  of  the  frenum  of  the  tongue.  These  ducts  are 
known  as  ^^harton's. 

The  siihlingval  glands  are  the  smallest  of  the  salivary  glands  and 
are  situated  above  the  floor  of  the  mouth,  in  the  sublingual  fossse  of 
the  mandible.  As  has  been  previously  stated,  their  ducts  join  with 
those  from  the  submaxillary  glands  and  make  their  entrance  into  the 
mouth  alongside  of  the  frenum  of  the  tongue. 

The  Fauces  and  the  Tonsils. — ^The  opening  leading  from  the  mouth 
to  the  pharynx  is  called  the  fauces.  It  is  bounded  above  by  the  soft 
palate,  below  by  the  base  of  the  tongue,  and  on  either  side  by  two 
pairs  of  muscles  which  receive  the  names  of  anterior  yiUars  and  pos- 
terior yUlars  of  the  fauces.  Between  these  two  pillars,  on  either  side, 
lie  the  faucial  tonsils.  These  are  lymph  nodes  which  probably  act 
as  filtering  plants  for  the  lymphatic  vessels  draining  the  mouth. 
\Yhatever  other  function  they  may  have  still  remains  a  mystery. 

There  are  two  other  masses  of  lymphoid  tissue  in  close  relationship 
to  the  mouth.  One  has  been  mentioned  under  the  description  of  the 
tongue.  This  is  called  the  lingual  tonsil.  The  other  is  known  as  the 
yharijngeal  tonsil  and  is  located  on  the  posterior  wall  of  the  pharynx, 
just  above  the  level  of  the  soft  palate  and  between  the  openings  of 
the  P^ustachian  tubes.  Enlargement  of  the  pharyngeal  tonsil  often 
occurs  in  children.  The  growth,  commonly  known  as  adenoids,  so 
completely  fills  the  upper  portion  of  the  pharynx  as  to  shut  oft'  the 
passages  into  the  nr)se  and  the  child  is  forced  to  breathe  through  the 
mouth.  Mouth-breathing,  when  continued  for  some  time,  produces 
very  characteristic  symptoms  chief  among  which  is  a  severe  oral 
deformity.  Blocking  of  the  orifices  of  the  Eustachian  tubes  by  these 
growths  often  produces  impairment  of  hearing. 

THE    TEETH. 

The  teeth  may  be  defined  as  the  calcified  structures  attached  to  the 
jaw-bones  })y  the  alveolar  i)rocesses  and  having  as  their  most  impor- 
tant function  tlie  breakingupof  food  material  in  preparation  for  digestion. 

'J'he  teeth  must  not  be  thought  of  as  a  i)art  of  the  osseous  system 
of  the  body  for  they  are  in  no  way  related  to  such  tissues  morpho- 
logically. Their  origin  and  structure  will  be  discussed  later  under 
J)evelo]jment. 


PLATE  VII 


A  Diagram  of  a  Section  througli  an   Incisor. 

Showing  the   bloodvessels   of  the  pulp  and    peridental   membrane.       The 
bone   is   represented   as  much   too  dense. 


THE  TEETH  79 

The  teeth  make  their  appearance  in  two  series  or  sets.  The  first, 
known  as  the  deciduous  (falling  off),  temporary  or  milk  teeth,  are 
twenty  in  number,  equally  divided  between  each  jaw,  and  named  as 
follows : 

Central  incisors. 

Lateral  incisors. 

Cuspids. 

First  molars. 

Second  molars. 
The  second  series  or  set,  known  as  the  permanent  teeth,  number 
thirty-two  when  complete.  The  increase  in  the  number  is  accounted 
for  by  the  following:  There  are  three  molars  on  each  side  in  the 
permanent  set  instead  of  two,  as  seen  in  the  deciduous.  Furthermore, 
these  are  all  three  erupted  behind  the  deciduous  molars.  The  latter 
are  replaced  when  shed  by  teeth  known  as  the  bicuspids.  It  is  there- 
fore to  be  noted  that  while  the  molar  teeth  in  the  deciduous  set  lie 
in  contact  with  the  cuspids,  the  molar  teeth  of  the  permanent  set  are 
separated  from  their  cuspids  by  two  teeth,  the  bicuspids.  The  per- 
manent teeth  are  therefore  named  as  follows: 

Central  incisors. 

Lateral  incisors. 

Cuspids. 

First  bicuspids. 

Second  bicuspids. 

First  molars. 

Second  molars. 

Third  molars. 
Occlusion. — The  teeth  are  arranged  in  two  gracefully  curving  arches, 
the  lower  of  which  is  somewhat  the  smaller  so  that  the  upper  overlaps 
it.  The  teeth  of  one  arch  do  not  meet  those  of  the  other  in  an  end- 
to-end  arrangement,  but  are  dovetailed,  as  it  were,  between  each 
other.  This  brings  broad  surfaces  in  contact  instead  of  mere  points. 
There  are  over  one  hundred  of  these  surfaces  that  are  in  contact  when 
all  the  teeth  are  present  and  in  their  proper  position.  These  surfaces 
are  known  as  inclined  planes  and  it  is  the  sliding  together  of  these 
various  inclined  planes  in  a  scissors-like  action  that  properly  prepares 
the  food  for  digestion. 

The  normal  arrangement  of  the  inclined  planes  of  the  teeth  when 
the  jaws  are  closed  is  known  as  occlusion  or  normal  occlusion  (Fig.  30). 
Li  this  arrangement  it  will  be  noted  that  every  tooth,  with  but  six 
exceptions,  is  in  contact  with  four  other  teeth,  i.  e.,  one  on  either  side 
of  it  and  two  in  the  opposing  arch.  The  teeth  excluded  from  this 
rule  are  the  lower  central  incisors  and  lower  third  molars  which  are 
in  contact  with  but  three  teeth,  and  the  upper  third  molars,  which 
are  in  contact  with  but  two  teeth. 

The  Anatomy  of  the  Tooth  (Plate  VII).— A  tooth  is  divided  into  two 
parts,  the  crown  and  the  root.    The  crown  is  that  portion  that  projects 


go 


SPECIAL  ANATOMY 


above  the  gum ;  the  root  is  that  portion  that,  under  normal  conditions, 
is  surrounded  by  gum  and  alveolar  process.  The  bulk  of  the  tooth 
is  made  up  of  calcified  connective  tissue  called  dentin.  The  crown 
portion  of  the  dentin  is  covered  by  the  hardest  tissue  in  the  body,  i.  e., 
the  enamel.  This  is  of  epithelial  or  lining  tissue  origin.  The  root 
portion  of  the  dentin  is  covered  with  a  calcified  connective  tissue 
that  more  closely  resembles  bone  than  any  of  the  other  tooth  tissues. 
It  is  called  the  cementum.  It  slightly  overlaps  the  enamel  at  the  gum 
margin. 


Fig.  30. — Normal  occlusi(;n.      (Turner.) 


In  the  center  of  the  dentin,  extending  the  whole  length  of  the  root 
and  more  or  less  into  the  crown,  is  a  cavity  called  the  pidp  cavity. 
This  contains  the  remains  of  the  organ  that  was  active  when  the 
tooth  was  being  formed  and  which  during  this  i)r()cess  deposited  the 
dentin.    This  organ  is  called  the  jjulj). 

'^I'he  i)ulp  c;avity  is  divided  into  two  parts,  that  in  the  crown,  known 
as  the  })iil)J  rharnhrr,  and  that  in  the  root  known  as  the  root  canal. 
The  root  canal  communicates  with  tlie  exterior  through  a  small  open- 
ing at  the  end  of  the  root.  This  opening  is  given  the  name  of  the 
apical  foramen.  .Sometimes  more  than  one  apical  foramen  is  found. 
Through  this  opening  tlu;  })l()odvessels  and  nerves  pass  to  the  pulp. 

Surrounding  the  root  and  separating  it  from  the  bony  wall  of  the 
socket  is  a  fibrous  membrane  known  as  the  peridental  membrane.    This 


THE   TEETH  81 

has  for  its  most  important  function  tiie  hindinj:;  of  the  tooth  to  the 
surrounding  bone.  The  l)()ne  that  supports  the  teeth  is  known  as 
the  alveolar  process.  This  is  formed  about  the  roots  of  the  teeth 
as  they  erupt.  When  a  tooth  is  removed  from  its  process  an  opening 
is  left  that  resembles  in  outline  the  shape  of  the  root.  This  cavity 
or  socket  is  called  an  (ilvcolus. 

Surmounting  the  alveolar  process  is  a  dense,  fibrous  connective 
tissue  called  the  gum.  This  is  covered  with  mucous  membrane  con- 
tinuous with  that  of  the  rest  of  the  mouth. 

Nomeficlahire. 

The  neck,  cervix  or  (jingival  margin  is  that  part  of  the  tooth  where 
the  enamel  and  cementum  meet. 

The  ape.v  is  the  end  of  the  root. 

The  occlusal  end  or  surface  is  the  top  of  the  crown,  /.  c,  that  portion 
of  the  tooth  used  in  mastication. 

A  cusp  is  a  projection  or  tubercle  on  the  surface  of  the  crown. 

The  pro.vimal  or  approximal  surface  is  that  surface  that  adjoins 
the  next  tooth.  The  most  prominent  point  of  this  surface  is  called 
the  point  of  contact  or  angle  of  the  tooth. 

The  mesial  surface  is  that  approximal  surface  that  is  nearest  the 
median  line  of  the  arch,  /'.  e.,  a  line  drawn  between  the  central  incisors. 

The  distal  surface  is  that  approximal  surface  that  is  farthest  away 
from  such  a  line. 

The  surface  of  the  incisors  and  cuspids  that  presents  toward  the 
lips  is  called  the  labial  surface.  The  corresponding  surface  on  the 
bicuspids  and  molars,  presenting  toward  the  cheeks,  is  termed  the 
buccal  surface. 

The  surface  of  the  upper  teeth  presenting  toward  the  palate  is 
called  the  palatal  surface.  The  corresponding  surface  on  the  lower 
teeth  presents  toward  the  tongue  and  is  called  the  lingual  surface. 
The  palatal  surface  of  the  upper  teeth  is  also  often  called  the  lingual 
surface. 

Descriptive  Anatomy  of  the  Various  Teeth. — The  Incisors  (Fig.  31). 
— The  crowns  of  these  teeth  are  wedge-shaped  with  the  sharp  edge 
downward.  They  present  four  surfaces  and  an  incisal  or  cutting  edge 
for  study. 

Labial  Surface. — This  is  convex  and  on  the  upper  incisors  is  irregu- 
larly quadrilateral  while  on  the  lower  it  is  more  of  a  triangle  in  out- 
line. There  are  usually  two  grooves  running  vertically  through  this 
surface,  known  as  the  demlopmental  grooves.  All  the  borders  of  this 
surface  are  more  or  less  convex,  that  at  the  gingivus  being  markedly 
so.  This  margin  also  ends  in  a  distinct  ridge.  The  mesio-incisal 
angle  is  quite  sharp  while  the  disto-incisal  angle  is  rounded. 

Lingual  or  Palatal  Surface. — This  is  irregularly  triangle  in  outline 
with  the  base  downward.  The  surface  is  concave  and  the  margins 
6 


82 


SPECIAL  ANATOMY 


are  outlined  with  ridges.  Sometimes  in  the  center  of  the  cervical 
ridge  is  a  rudimentary  cusp  at  the  base  of  which  is  a  depression  or  pit. 

Mesial  and  Distal  Surfaces. — In  outline  these  resemble  arrow  heads 
and  their  general  surface  is  convex.  They  presei^t  two  concave  mar- 
gins, the  lingual  and  gingival,  and  one  convex,  the  labial. 

Incisal  Edge. — The  plane  of  this  surface  is  more  or  less  at  a  right 
angle  to  the  crown.  It  is  of  varying  thickness  and  in  newly  erupted 
teeth  presents  three  tubercles.  These  quickly  wear  off  as  the  teeth 
are  used. 


Fig.  31. — Left  upper  central  incisor.     Labial  surface.      (Johnson.) 


The  roots  are  cone-shaped  with  the  labiolingual  diameter  greater  than 
the  mesiodistal.  In  the  lower  teeth  the  roots  are  even  more  flattened 
mesiodistally  than  in  the  upper.  The  apex  of  the  root  often  has  a 
slight  distal  })end. 

Each  ]tv]p  cavity  follows  roughly  in  outline  the  shape  of  the  tooth. 

Individual  Characteristics  of  the  Incisors. —  Upper  Central.  This  is 
the  largest  of  the  incisors.  Its  root  is  shorter  and  thicker  than  that  of 
the  others.  Upper  lateral.  The  distal  surface  of  the  crown  of  this 
tooth  is  very  convex  so  that  the  point  of  contact  is  (}uite  i)rominent 
and  the  incisal  edge,  oblique.  Its  root  is  the  longest  of  the  incisor 
roots.     Lower  Central.    This  is  the  smallest  of  the  incisors. 

The  Cuspids  fFig.  32). — The  crowns  of  these  teeth  present  for  study 
four  surfaces  and  an  incisal  edge  that  takes  the  form  of  a  cusp. 


THE   TEETH 


83 


Labial  Surface. — This  is  very  convex  and  is  marked  with  two 
developmental  grooves  between  which  is  a  prominent  ridge.  It  has 
five  borders  as  follows:  two  approximal,  two  incisal  and  one  cervical. 
The  api)roximal  and  the  cervical  are  con\'ex,  while  the  incisal  are 
usually  quite  straight.  The  disto-incisal  border  is  the  longer  of  the 
two. 

Lingual  Surface. — This  is  similar  in  outline  to  the  labial  and  also 
presents  a  vertical  ridge  riuming  through  the  center.  The  cervical 
end  of  this  ridge  is  frequently  marked  with  a  tubercle. 


Fig.  32.  —  Right  upper  cuspid. 
Labial  surface.      (Johnson.) 


Fig.  33. — Right  upper  second  bicuspid. 
Mesial  surface.     (Johnson.) 


The  mesial  and  distal  surfaces  are  similar  in  outline  to  the  corre- 
sponding surfaces  of  the  incisors  but  "are  of  greater  dimensions  labio- 
lingually. 

llie  Incisal  Edge. — This  is  in  the  form  of  two  planes,  a  mesial  and 
a  distal.  The  distal  is  the  longer  of  the  two.  At  their  point  of  union 
they  are  joined  by  the  labial  and  lingual  ridges  of  the  surfaces  of  the 
same  name,  to  form  the  cusp. 

The  roots  are  conical,  flattened  mesiodistally  and  sometimes  even 
concave  on  these  sides.  A  distal  bend  at  the  apex  is  quite  common. 
The  upper  cuspid  has  the  longest  root  of  any  tooth  in  the  mouth. 

Each  pvlp  cavity  has  the  same  general  outline  as  the  tooth. 


84  SPECIAL  ANATOMY 

Distinguishing  Points  between  the  Upper  and  Lower  Cuspids. — The  crown 
of  the  lower  cuspid  is  more  delicate  in  shape  and  slightly  longer  than 
the  u])])er.  Its  root  is  shorter  and  more  flattened  mesially  and  distally. 

The  Bicuspids  (Fig.  33). — ^The  crowns  of  these  teeth  are  irregularly 
cuboidal  in  form  and  present  five  surfaces  for  study,  i.  e.,  buccal, 
lingual,  mesial,  distal  and  occlusal. 

The  buccal  surface  is  convex,  is  bounded  by  five  borders,  and  closely 
resembles  the  corresponding  surface  of  a  cuspid  but  is  somewhat 
shorter  than  this  tooth  in  its  verticle  dimension. 

The  lingua]  surface  has  the  same  general  characteristics  as  the 
buccal  but  is  smaller  in  all  its  dimensions. 

The  mesial  surface  is  irregularly  quadrilateral  and  slightly  convex. 
Its  buccal  and  lingual  borders  are  convex,  the  lingual  being  consider- 
ably the  shorter  of  the  two.  The  cervical  and  occlusal  borders  are 
concave.  The  occlusal  border  of  the  upper  bicuspids  is  quite  "V" 
shaped,  the  apex  of  the  "V"  being  between  the  cusps. 

The  distal  surface  closely  resembles  the  mesial  but  is  much  more 
convex.  • 

Occlusal  Surface. — In  outline  this  surface  is  somewhat  egg-shaped. 
It  presents  for  study  two  cusps,  a  central  groove  and  a  mesial  and 
distal  border.  The  cusjjs  are  placed  buccally  and  lingually,  the  buccal 
being  the  larger  one.  Each  cusp  has  four  inclines  or  inclined  planes, 
as  they  are  usually  called.  These  are  named  from  the  surface  toward 
which  they  slope,  ;'.  e.,  mesial,  distal,  buccal  and  lingual.  The  groove 
runs  mesiodistally  and  separates  the  cusps.  The  mesial  harder  is  nearly 
straight  while  the  distal  border  is  decidedly  convex.  Both  of  these 
borders  are  surmounted  with  ridges. 

The  Roofs. — The  upper  first  bicuspid  has  two  roots.  Of  these  the 
buccal  is  the  larger.  All  the  other  bicuspids  have  but  one  root.  The 
buccolingual  dimension  of  the  root  is  the  greater.  Its  mesial  and 
distal  sides  are  concave.  A  distal  curve  to  the  apex  of  the  root  is 
common. 

The  Pul])  Cariiy. — The  jmli)  chamber  can  be  more  readil\'  outlined 
in  the  bicuspids  than  in  the  incisors  or  cuspids.  Its  form  follows 
roughly  that  of  the  crown  while  the  shape  of  the  yuly  canal  corre- 
sponds to  that  of  the  root.  The  upper  first  bicuspids  have  two  pulp 
canals,  the  other  bicuspids  usually  have  })ut  one,  although  two  may  be 
found. 

Individual  Characteristics  of  the  Bicuspids. — The  upper  first  is  the 
largest  of  the  bicuspids.    It  has  two  roots  and  two  root  canals. 

The  lower  fir. "ft  is  the  smallest  of  the  bicus])ids.  Its  lingual  cusp  is 
very  rudimentary.  Its  root  is  broad  mesiodistally  on  the  buccal  side 
and  quite  narrow  on  the  lingual  sifle. 

The  Upper  Molars  (I'ig.  34). — The  crowns  of  these  teeth  are  irregu- 
larly cuboidal,  presenting  the  same  five  surfaces  for  study  as  do  the 
bicuspids.  The  crowns  of  the  molars  are  smaller  in  diameter  at  the 
neck  than  at  their  occlusal  border. 


TlIK   TEEril 


85 


The  huccdl  surfdcc  is  ^ciicriilly  coin'ex  and  is  (liN'idcd  vertically  by 
a  groove.  Often  in  the  center  ot"  this  surface  is  a  })it.  When  this  is 
present  the  buccal  groo\e  usually  terminates  in  it.  The  buccal  sur- 
face has  four  borders.  Of  these  the  occlusal  is  the  most  striking  in 
that  it  is  marked  with  two  cusps. 

The  Jin(/u(tl  surface  resembles  the  buccal  very  closely  exee])t  that 
the  mesial  and  distal  margins  converge  more  at  the  cervix  as  they 
are  continued  into  one  root  instead  of  two  as  is  the  ease  with  corre- 
sponding margins  of  the  buccal  surface. 

The  mesial  .s'lirface  at  the  occlusal  third  is  convex  while  the  gingival 
two-thirds  is  straight  or  concave. 


Fig.  34. — Left  upper  fir.st  molar.     Bueeal  surface.      (Johnson.) 


The  distal  surface  is  similar  to  the  mesial,  though  perhaps  in  general 
a  little  more  convex. 

The  occlusal  surface  is  irregularly  rhombf)idal,  the  acute  angles 
being  the  mesiobuccal  and  the  distolingual.  It  presents /o?/r  cusps, 
two  of  which  are  buccal,  called  the  mesiobuccal  and  distobuccal  cusps, 
and  two  lingual,  called  the  mesiolingual  and  the  distolingual  cusps. 
The  mesiolingual  is  the  largest  cusp.  Running  obliciuely  across  the 
occlusal  surface  there  is  in  succession  a  groove,  a  ridge,  and  a  second 
groove.  The  first  groove  begins  in  the  middle  of  the  mesial  margin, 
and  passes  distally  and  buccally  across  the  occlusal  surface  to  the  inter- 
val between  the  two  cusps  where  it  is  continued  over  onto  the  buccal 
surface  as  the  buccal  groove.    The  ridge  runs  from  the  mesiolingual 


86  SPECIAL  ANATOMY 

cusp  to  the  distobuccal  cusp.  The  second  groove  begins  between  the 
two  Hngual  cusps  as  a  continuation  of  the  hngual  groove  and  runs 
distally  and  buccally  to  the  center  of  the  distal  margin.  Just  mesial 
and  distal  to  the  center  of  the  oblique  ridge  oxefosscB. 

The  Roots. — These  are  three  in  number,  two  being  placed  buccally 
and  one  lingually.  The  lingual  is  the  largest  root  and  the  distobuccal 
the  smallest.  The  apices  of  the  two  buccal  roots  tend  to  converge 
toward  each  other. 

The  Pulp  Cavity. — The  outline  of  the  pulp  chamber  resembles  the 
form  of  the  crown.  On  the  floor  of  this  chamber  are  three  openings 
leading  into  the  three  root  canals. 

Individual  Characteristics  of  the  Upper  Molars. — The  first  molar  is  the 
largest  of  the  upper  molars.  It  is  often  distinguished  by  the  fact  that 
it  has  a  fifth  cusp  situated  at  the  mesio-occlusal  corner  of  the  lingual 
surface.  This  is  ver}'  small  and  rudimentary.  The  roots  of  the  first 
molar  are  usually  larger  and  diverge  from  one  another  to  a  greater 
degree  than  in  the  other  upper  molars. 

The  second  molar  is  often  quite  flattened  mesiodistally.  It  never  has 
the  fifth  cusp.     Frequently  the  buccal  roots  show  a  distal  inclination. 

The  third  molar,  with  the  lower  third  molar,  is  the  most  variable 
tooth  in  the  head.  If  t^-pical  it  should  present  but  three  cusps,  the 
distolingual  being  lost.  It  has  no  oblique  ridge,  but  presents  instead 
a  central  fossa.  There  may  be  three  roots  or  there  may  be  but  one, 
and  the  root  canals  vary  with  the  number  and  position  of  the  roots. 

The  Lower  First  Molar  (Fig.  35). — ^The  crown  of  this  tooth  is  also 
irregularly  cuboidal,  and  presents  five  surfaces  for  study. 

The  buccal  surface  differs  from  the  buccal  surface  of  the  upper 
molars  in  that  it  is  longer  mesiodistally  and  presents  two  grooves 
instead  of  one.  Its  occlusal  border  is  surmounted  by  three  cusps 
instead  of  two. 

The  Unr/iial,  mesial  and  distal  surfaces  all  resemble  the  corresponding 
surfaces  of  the  upper  first  molar. 

The  Occlusal  Surface. — ^This  differs  considerably  from  the  corre- 
sponding surface  of  the  upper.  It  is  trapezoidal  in  outline  with  the 
long  side  buccally  and  is  marked  with  five  cusps,  five  grooves  and  a 
central  fossa.  The  cusps  are  arranged  three  l)uccally,  named  from 
mesial  to  distal,  mesiobuccal,  buccal  and  distobuccal;  and  two  lin- 
gually, named  mesiolingual  and  distolingual.  The  grooves  radiate 
from  the  central  fossa  and  are  named  mesial,  buccal,  distobuccal 
(between  the  buccal  and  distobuccal  cusps),  distal  and  lingual.  The 
mesiol)Uccal  cusp  is  the  largest  and  the  distobuccal  the  smallest. 

The  Roots. — These  are  two  in  number  and  are  placed  one  mesially 
and  the  other  distally  and  are  known  by  these  names.  They  present 
a  distal  inclination.    The  mesial  root  is  the  larger. 

The  Pnl]j  Cavity. — The  pvljj  chamber  resembles  in  outline  the  crown. 
The  pvlp  canals  are  frequently  three  in  miinbcr  there  often  being  two 
in  the  large  mesial  root. 


THE   TEETH 


87 


The  Lower  Second  Molar, — This  resembles  the  first  lower  molar  but 
is  a  smaller  tooth  and  has  but  four  cusps,  the  distobuccal  being  absent. 
The  cusp  corresponding  to  the  buccal  cusp  of  the  first  molar  receives 
the  name  of  distobuccal  in  the  second  molar. 

The  occhisdl  surf  (ice  presents  a  central  fossa  and  four  grooves  radi- 
ating from  it. 

The  roots  are  somewhat  smaller  and  are  situated  close  together. 
But  two  root  canals  is  the  usual  order.  The  roots  have  a  marked  distal 
inclination. 


Fig.  35. — Right  lower  first  molar.     Buccal  surface.      (Johnson.) 


The  Lower  Third  Molar. — This  is  extremely  variable  in  form  but 
when  typical  should  resemble  the  second  molar  in  miniature. 

Descriptive  Anatomy  of  the  Deciduous  Teeth. — The  deciduous  teeth 
resemble  the  permanent  teeth  in  their  general  form  but  are  of  course 
much  smaller.  Their  cusps,  are  not  as  well  defined  and  the  form  of  the 
molars  and  cuspids  is  such  that  they  are  larger  at  the  neck  than  at  the 
occlusal  border. 

The  incisors  and  cusijids  are  very  much  like  the  corresponding 
teeth  in  the  permanent  denture;  the  loiver  first  molars  quite  closely 
resemble  the  lower  second  permanent  molars;  the  second  molars, 
both  upper  and  lower,  are  similar  in  design  to  the  upper  and  lower 
first  permanent  molars;  the  upper  first  molars,  however,  are  different 
in  certain  respects  from  any  of  the  other  teeth  and  therefore  require 
a  more  detailed  description. 


88  SPECIAL  ANATOMY 

The  Upper  First  Deciduous  Molar. — The  ccclusal  surface  presents 
three  cusps,  two  buecally  and  one  Hngually.  The  latter  is  so  large, 
however,  that  it  makes  this  side  about  as  long  mesiodistally  as  the 
luKcal.  This  surface  presents  a  central  fossa  with  three  grooves 
radiating  from  it,  i.  e.,  a  mesial,  a  buccal  and  a  distal. 

The  buccal  surface  resembles  that  of  any  upper  molar;  the  lingual 
is  very  convex  and  has  no  groove;  the  mesial  and  distal  are  convex 
at  their  cervical  borders. 

Approximate  Age  at  which  the  Various  Teeth  Erupt. — Lower  teeth 
erupt  before  the  upper  as  a  rule. 

The  Deciduous  Denhtre. 

Central  incisors,  6th  to  8th  month. 
Lateral  incisors,  8th  to  10th  month. 
First  molars,  lOth  to  16th  month. 
Cuspids,  16th  to  20th  month. 
Second  molars,  20th  to  30th  month. 

The  Permanent  Denture. 

First  molars,  5th  to  7th  year. 
Central  incisors,  6th  to  8th  year. 
Lateral  incisors,  7th  to  9th  year. 
First  bicuspids,  8th  to  10th  year. 
Lower  cuspids,  9th  to  11th  year. 
Second  bicuspids,  10th  to  12th  year. 
Upper  cuspids,  11th  to  13th  year. 
Second  molars,  12th  to  14th  year. 
Third  molars,  17th  year  to  any  time  later. 

HISTOLOGY  OF  THE  TEETH  AND  ASSOCIATED  STRUCTURES.^ 

The  Enamel. — This  is  the  only  calcified  tissue  in  the  body  that  is 
derived  from  epithelial  structures.  All  others  have  their  origin  in  con- 
nective tissue.  Enamel  is  also  the  hardest  of  the  tissues  and  contains 
no  organic  matter.  Chemically  it  is  made  up  for  the  most  part  of 
ph(jsphate  and  carbonate  of  lime.  As  there  is  no  organic  matter  to 
})e  found  in  its  make-up  it  must  be  designated  as  a  dead  tissue.  The 
epithelial  cells  that  are  active  in  its  formation  are  destroyed  when 
their  work  is  finished. 

Enamel  is  composed  of  two  structural  elements:  (a)  Enamel 
prisms  or  rods,  and  (6)  a  cementing  substance. 

The  Enamel  Rod  (Fig.  36). — These  are  prismatic  in  form,  having 
five  or  six  sides  and  their  average  diameter  is  about  one-half  that  of 
a  red  blood  corpuscle.  Throughout  their  entire  length  we  find  them 
alternately  constricted   and  expanded.     When   placed  side  by  side 

'  A  resum^  from  Dental  Histology  and  Embryology  by  Dr.  F.  B.  Noyes. 


HISTOLOaV  OF   TOOTH  STRUCTURES 


89 


these  ex])ansi()ns  and  constrictions  are  not  (lo\'ctailc(l  into  each  other, 
but  are  arran<;e(l  opjjosite  one  another. 

The  (U'liieiitiiK)  Siihsfance. — Between  the  rods  and  fillinii;  np  the 
spaces  made  by  this  peculiar  arranj^ement  of  the  prisms,  is  the  cement- 
ing substance.  This  cementing  substance  is  also  highly  calcified  but 
is  more  susceptible  to  injury  than  the  prisms.  When  enamel  cracks 
the  line  of  cleavage  runs  through  the  cementing  substance  and  not 
across  the  rods.  When  an  acid  is  brought  in  contact  with  the  enamel 
the  cementing  substance  is  destroyed  before  the  rods. 

The  enamel  is  formed  from  within  outward  so  that  on  the  surface 
of  the  tooth  is  the  last  enamel  that  is  laid  down.  The  prisms  extend 
from  the  dentin  outward  and  are  arranged  in  a  manner  that  will 


Fig.  .36. — Enamel  rod.s  in  thin  etched  section.      (About  800  X.)      (Xoye.s.) 


best  resist  the  force  that  is  brought  upon  them  as  the  teeth  are  used. 
The  prisms  do  not  always  run  in  a  straight  line  from  the  dentin  to 
the  surface  but  in  many  places,  especially  where  the  stress  is  great, 
such  as  on  the  cusps  of  the  teeth,  they  are  intertwined  with  one  another 
something  like  the  strands  of  a  rope.  Such  enamel  is  called  gnarled 
enamel.  Straight  enamel  is  that  in  which  the  prisms  run  in  practically 
a  straight  line  from  the  dentin  to  the  surface. 

In  sections  of  enamel  two  kinds  of  markings  are  distinguished  on 
the  cut  surface:  (o)  striation  and  (6)  stratification.  The  striatlon 
is  quite  like  that  of  voluntary  muscle  fibers  and  is  due  to  the  alter- 
nating expansion  and  contraction  segments  of  the  rods.  The  strati- 
fication  is  seen  in  longitudinal  sections  only.     It  consists  of  dark 


90 


SPECIAL  ANATOMY 


bands  running  through  the  enamel.  These  are  due  to  pigment  being 
deposited  in  the  enamel  as  it  is  formed.  A  portion  of  the  enamel 
having  been  formed,  upon  the  surface  of  this  is  deposited  pigment. 
Following  this  another  layer  of  enamel  is  laid  down  upon  which  is 
deposited  more  pigment,  etc.  These  lines  of  stratification  are  there- 
fore an  index  as  to  just  how  the  enamel  is  laid  down  and  show  that 
the  first  layer  is  deposited  at  the  occlusal  end  of  the  crown  and  suc- 
cessive layers  work  their  way  rootward. 

When  a  tooth  first  erupts  it  is  covered  with  a  thin  membrane  called 
Xa^'imyth's  membrane.  This  is  the  remains  of  the  enamel  organ,  active 
during  the  formation  of  this  tissue.  It  soon  wears  off  as  the  tooth  is 
brought  into  use. 


■If  K 


Fig.  37. — Dentin  showing  tubules  in  cross-section:    Dl,  dentinal  tubules;   D,  dentin 
matrix;    .S,  shadow  of  sheaths  of  Newman.     (About  1150  X.)      (Noyes.) 

Functions  of  the  Enamel. — (a)  It  covers  the  exposed  portion  of 
the  tooth  and  prevents  irritation  of  the  underh^ing  sensative  dentin. 

(h)  By  its  hardness  it  resists  abrasion  from  the  force  of  mastication. 
Enamel  differs  from  any  other  calcified  tissue  in  the  following  details: 

(a)  It  is  formed  by  epithelial  cells. 

ih)  It  contains  no  organic  material  either  in  the  form  of  cells  or 
intercellular  substance. 

(c)  The  organ  that  forms  it  disai)pears  after  its  work  is  complete. 

{(l)  It  is  made  of  ])risms  cemented  together.  All  other  calcified 
tissue  has  fibrous  connective  tissue  as  its  structural  basis. 

The  Dentin  (Fig.  'M). — Dentin  is  a  calcified  connective  tissue  and 
is  used  to  make  up  the  bulk  of  the  tooth.  It  contains  considerable 
organic  matter  and  yields  gelatin  when  l)oiled.  Its  iiiovf/atiic  matter  is 
mostly  carbonate  and  phosphate  of  lime. 


HISTOLOGY  OF  TOOTH  STRUCTURES  91 

Structurally  (kMitin  is  made  u\)  of  the  following  elements: 

(a)  Dentin  matrix. 

(b)  The  dentinal  tubules  with  their  walls  which  latter  structures 
are  known  under  the  name  of  the  "sheaths  of  Neuman." 

(c)  The  dentinal  fibrils. 

The  Dentin  Matrix. — This  is  a  homogeneous  material  that  is  very 
elastic.  As  seen  with  the  imaided  eye  it  is  yellowish.  It  is  composed 
of  about  one-third  organic  material  and  two-thirds  inorganic  in  the 
form  of  lime  salts. 

The  Dentinal  Tuhvles. — Extending  throughout  the  matrix  and 
radiating  from  the  pulp  cavity  are  minute  tubes.  These  take  a  spiral 
course  in  their  passage  through  the  matrix.  They  also  intercommuni- 
cate with  one  another.  They  end  at  the  dento-enamel  or  dento- 
cemental  junction.  At  the  former  junction  they  branch  close  to  their 
termination  in  delta-like  formations.  These  deltas  are  in  communi- 
cation with  one  another.  This  intimate  interconnection  of  many 
tubules  explains  why  the  dento-enamel  junction  is  such  a  sensitive 
area  under  the  action  of  instruments.  At  the  dentocemental  junction 
the  tubules  open  into  spaces  lying  between  the  cement  and  the  dentin. 
These  spaces,  ranging  as  they  do  along  the  whole  length  of  the  root, 
form  what  is  known  as  the  ''granular  layer  of  Tomes."  (Fig.  38.) 

The  matrix  immediately  surrounding  the  tubules  is  of  a  more  dense 
composition  than  that  in  other  parts.  This  densely  formed  portion 
receives  the  name  of  the  sheath  of  Neuman.  The  name  is  somewhat 
misleading  for  it  is  not  a  true  membrane,  but  is  undoubtedly  a  special- 
ized portion  of  the  matrix  itself  forming  a  wall,  as  it  were,  to  the  tubes. 
It  has  been  found  that  the  sheaths  of  Neuman  have  considerable 
elastin  as  one  of  their  component  elements. 

The  Dentinal  Fibrils. — These  are  the  protoplasmic  processes  found  in 
the  tubules  and  are  extensions  from  the  cells  of  the  pulp  that  were 
active  in  the  formation  of  the  dentin.    These  cells  are  called  odontoblasts. 

Function  of  the  Dentin. — (a)  Forms  the  great  bulk  of  the  tooth. 

(b)  Acts  as  an  elastic  cushion  to  the  enamel  so  that  this  tissue  will 
not  break  under  stress. 

(c)  Gives  strength  to  the  whole  tooth. 

The  Cementum  (Fig.  08). — This  is  also  a  calcified  connective  tissue. 
It  more  nearly  resembles  bone  than  does  the  dentin.  It  is  arranged 
in  consecutive  layers  around  the  tooth  root  and  slightly  overlaps  the 
enamel  at  the  cervical  margin. 

Structurally  cementum  is  made  up  of  the  following  elements: 

(a)  The  lamella?. 

(b)  The  lacunae  from  which  radiate  the  canaliculi. 

(c)  Cement  cells  or  corpuscles. 

(d)  The  embedded  fibers  of  the  peridental  membrane. 

The  LamelloB. — This  is  the  name  given  to  the  layers  of  cementum. 
These  vary  in  thickness  according  to  the  position  on  the  root,  being 
thinest  at  the  gingival  margin  and  thickest  at  the  apex.     They  are 


92 


SPECIAL  ANATOMY 


arranged  concentricallx'  about  the  root.  There  is  a  continuous  forma- 
tion of  cementum  ji;oing  on  throughout  Hfe  so  that  the  older  the  indivi- 
dual, the  more  layers  of  cementum  there  will  be.  By  virtue  of  this 
property  of  continuous  formation  the  cementum  is  the  one  tissue  of 
the  tooth  that  is  capable  of  repairing  itself  after  injury.  Destruction 
of  the  dentin  on  the  surface  of  the  root  may  also  be  repaired  by  the 
cement  cells  filling  in  such  areas  with  cementum. 


Kk;.  .'•is. — Two  fields  of  (•ciiiciitiiiii  showing  ppii«<'al iiig  fihcis:    GT,  tinuiular  layer  of 
Tomes:  C,  comontuni  not  .showiiiK  fibers;  F,  pcnctralinK  fillers.    (About  54  X.)    (Noyes.) 

The  Lnnnifr. — The  lacuna^  arc  mimite  si)aces  scattered  throughout 
the  cementum,  being  both  in  the  substance  of  the  lamclhe  and  between 
the  various  layers.  From  these  radiate  in  all  directions  minute  canals 
called  cunalicvli.  These  canaliculi  intercommunicate  with  those 
from  the  adjacent  lacunje.  The  cement  rell.s  or  corjnificle.s  lie  in  the 
iacunte.  They  arc  the  cells  that  are  active  in  tiic  forination  of  cemen- 
tum.   Their  protoplasmic  processes  extend  into  the  canaliculi. 


THE  DENTAL   PULP  93 

The  Kinbrddcd  Fibcr.s-  of  the  Peridental  iMeiiibrane.-ThL'  cement 
cells  previous  to  the  formation  of  cementum  are  located  in  the  mem- 
brane that  surrounds  the  root,  the  peridental  membrane.  The  cement 
is  built  from  within  outward,  /.  e.,  that  nearest  the  dentin  is  the  first 
to  be  formed.  x\s  these  cells,  called  cementoblasts  when  active,  form 
the  various  lamelhe  they  build  themselves  into  the  structure  that  they 
are  forming.  In  this  process  many  of  the  fi})ers  of  the  peridental 
membrane  are  also  built  into  the  cementum  and  after  a  time  become 
more  or  less  calcified.    These  constitute  the  eml)e(lded  fibers. 

On  the  opposite  side  of  the  peridental  membrane,  /.  e.,  that  side 
that  is  in  relationship  to  the  bone  of  the  alveolus,  we  find  that  fibers 
of  the  membrane  are  similarly  built  into  the  bone.  Through  the  agency 
of  all  these  embedded  fibers  the  tooth  is  firmly  held  in  its  socket. 

The  Function  of  the  Cenienturn. — It  is  the  tissue  which  through  its 
ability  to  attach  the  tooth  to  the  surrounding  connective  tissue,  holds 
it  in  position.  The  cementum  may  therefore  be  considered  as  the 
most  important  of  the  tooth  tissues. 

The  Pulp. — This  is  the  structure  occupying  the  cavity  within  the 
dentin.  It  represents  the  remains  of  the  organ  that  was  active  when 
the  dentin  was  formed. 

Structurally  the  pulp  is  made  up  of  the  following  elements: 

(a)  Odontoblasts. 

(b)  Connective-tissue  cells. 

(c)  Intercellular  tissue. 

(d)  Bloodvessels. 

(e)  L\Tiiphatics. 
(/)  Nerves. 

The  Odontoblasts. — These  are  the  specialized  connective-tissue  cells 
that  form  the  dentin.  They  lie  along  the  periphery  of  the  pulp  in 
contact  with  the  dentin  walls  and  send  long  protoplasmic  processes 
into  the  dentinal  tubules. 

The  Connectire-t'.ssue  Cells. — These  are  stellate  in  form  and  resemble 
the  connective-tissue  cells  in  young,  growing  tissue.  They  are  scattered 
throughout  the  pulp  tissue. 

The  Intercellular  Substance. — This  is  quite  structureless  and  gelat- 
inous in  character.  Scattered  everywhere  through  it  are  the  cells 
just  described. 

The  Bloodvessels. — These  enter  the  tooth  through  the  apical  foramen 
and  the  larger  vessels  travel  through  the  center  of  the  pulp,  giving  oflf 
many  branches.  These  break  up  into  capillaries  which  form  a  rich 
network  about  the  periphery  of  the  pulp.  From  these  the  blood  is 
collected  by  veins  that  run  with  the  arteries  and  pass  out  through  the 
foramen.  The  walls  of  the  bloodvessels  in  the  pulp  are  extremely 
thin  even  in  the  arteries  and  larger  veins.  This  condition  renders  the 
tissue  particularly  susceptible  to  inflammation. 

The  Lymphatics. — Within  the  last  year  Dr.  Noyes  has  succeeded 
in  dem.onstrating  that  there  are  hinphatic  vessels  in  the  pulp  and 


94  SPECIAL  ANATOMY 

that  these  are  connected  through  the  apical  foramen  with  the  lymphatic 
vessels  and  glands  of  the  neck. 

The  Nerves.  —  Several  trunks  enter  the  tooth  through  the  apical 
foramen  and  run  through  the  center  of  the  pulp  giving  off  branches. 
These  branches  pass  to  the  periphery  and  form  a  network  at  the 
base  of  the  odontoblasts  and  secondary  arborizations  around  each 
odontoblast.  None  of  the  nerve  fibrils  enter  the  tubules  in  the  dentin. 
Sensation  in  the  dentin  is  due,  therefore,  to  the  irritation  of  the  proto- 
plasmic processes  of  the  odontoblasts  which  transfer  these  irritations 
to  the  nerve  fibers  in  physiological  contact  with  them. 

Function  of  the  Pulp. 

(a)  The  formation  of  dentin. 

(6)  A  sensory  function.  It  responds  to  heat,  cold,  and  gives  the 
sensation  of  pain. 

Secondary  Dentin. — This  is  dentin  that  is  sometimes  formed  after 
the  normal  amount  of  dentin  has  been  laid  down  and  the  pulp  has 
ceased  to  functionate.  It  is  due  to  irritation  of  the  pulp  by  some 
external  agent  and  this  organ  responds  by  attempting  to  again 
perform  the  duties  for  which  it  was  designed. 

The  Attachment  of  the  Teeth. — As  has  been  previously  stated,  the 
teeth  are  not  to  be  considered  a  part  of  the  osseous  system  of  the 
body,  as  they  bear  no  relation  to  it  from  a  point  of  origin.  Of  what 
system  then  are  they  a  part?  It  has  been  clearly  proved  that  these 
organs  are  appendages. of  the  skin  that  have  through  the  processes 
of  evolution  become  highly  specialized  into  the  form  that  we  see  them 
in  the  various  animals  and  in  man.  The  simplest  form  of  tooth  is 
seen  in  some  of  the  fishes.  It  consists  of  a  cone  of  enamel  covering  a 
calcified  connective-tissue  papilla  containing  tubules  and  closely 
simulating  dentin.  This  in  turn  rests  upon  a  second  mass  of  calcified 
connective  tissue  like  unto  the  cementum.  Into  this  latter  structure 
the  fibers  of  the  underlying  tissue  are  built.  To  such  a  simple  form  of 
tooth  no  bone  is  in  any  way  related.  In  the  attempt  to  find  from  what 
structures  the  teeth  were  evolved  it  was  noted  that  the  dermal  scales 
on  the  bodies  of  certain  fish,  ?'.  e.,  the  shark  and  sturgeon,  were  but 
duplicates  of  the  simple  forms  of  teeth  just  described.  This  fact, 
together  with  other  sufficient  proof,  left  no  question  but  that  the  teeth 
were  really  dermal  appendages  that  had  migrated  into  the  mouth. 

From  this  simple  form  of  tooth  attachment  by  fibrous  tissue  to 
underlying  soft  parts  there  are  numerous  variations  of  form  and 
methods  of  attachment  according  to  the  work  that  the  individual 
requires  of  his  teeth  and  the  amount  of  force  exerted  upon  them  in 
doing  this  work.  So  it  is  noted  that  as  the  food  upon  which  an 
animal  subsides  becomes  harder,  the  attachment  of  the  teeth  becomes 
firmer.  To  combat  the  force  of  dis])hi('('mciit,  roots  were  evolved  and 
bone  developed  about  tliein  until  the  jx-rfectcd  form  of  support,  as 
seen  in  man,  was  reached. 

At  first  thought  it  might  seem  that  the  strongest  way  in  which  to 


THE  PERIDENTAL  MEMBRANE  95 

hold  a  tooth  in  place  would  be  to  build  the  bone  immediately  against 
the  root  so  as  to  lock  the  tooth  absolutely  in  position.  If  this  were 
done,  however,  the  slightest  blow  upon  the  crown  of  a  tooth  would 
either  fracture  it  at  the  gingival  margin  or  so  severely  shock  the  pulp 
that  its  life  would  be  forfeited.  Furthermore,  the  transmission  of 
the  force  of  mastication  to  the  bones  of  the  head  under  such  favorable 
conditions  would  be  productive  of  severe  traumatic  shock  to  the  brain. 
Nature  avoids  all  of  this  by  placing  between  the  root  of  the  tooth  and 
the  bone  of  the  alveolar  process  a  fibrous  membrane,  the  function  of 
which  is  to  literally  suspend  the  tooth  in  its  socket.  Thus  it  not  only 
retains  the  tooth  perfectly  but  also  acts  as  a  cushion.  This  membrane 
is  called  the  peridental  memhrcme  and  may  be  considered  as  the  most 
important  of  all  the  dental  tissues.  Why?  Because  it  makes  no  dif- 
ference how  perfectly  formed  a  tooth  is  or  how  carefully  its  contour 
be  restored  by  dental  operations  correcting  the  ravishes  of  caries,  if 
this  membrane,  that  bears  all  the  stress  during  mastication,  is  not  in 
perfect  health,  that  tooth  will  be  proportionately  useless. 

The  Peridental  Membrane. — Definition. — The  peridental  membrane 
may  be  defined  as  that  tissue  which  fills  the  space  between  the  surface 
of  the  root  and  the  bony  wall  of  its  alveolus,  surrounds  the  root  occlu- 
sally,  from  the  border  of  the  alveolus,  and  supports  the  gum.    (Noyes.) 

From  this  definition  it  will  be  noted  that  this  membrane  not  only 
covers  that  portion  of  the  root  that  is  within  the  alveolus  but  also 
that  part  between  the  top  of  the  alveolus  and  the  gingival  line.  Indeed 
this  latter  portion  may  be  considered  as  the  most  important  part  of 
the  membrane,  because  it  is  here  that  the  initial  lesions  which  eventually 
lead  to  the  loss  of  the  tooth,  occur. 

Structurally  the  peridental  membrane  is  made  up  of  the  following 
elements : 

White  fibrous  connective  tissue. 
Four  varieties  of  cells: 
Fibroblasts 
Cementoblasts. 
Osteoblasts. 
Osteoclasts. 
Bloodvessels. 
Nerves. 
Epithelial  structures. 

The  White  Fibrous  Connective  Tissue. — A  careful  study  of  the  distri- 
bution of  this  tissue  is  of  absolute  necessity  if  one  is  to  realize  the 
important  role  that  the  peridental  membrane  plays  in  maintaining 
the  tooth  in  a  functionating  condition. 

The  fibrous  tissues  may  be  divided  into  two  classes  of  fibers:  (a) 
The  principal  and  (6)  the  indifferent.  The  first  group  is  the  one 
concerned  in  the  support  of  the  tooth,  the  other  fibers  simply  fill 
the  spaces  between  the  principal  fibers  and  support  the  blood- 
vessels. 


96  SPECIAL  ANATOMY 

The  Principal  Fibers, — These  are  built  into  the  cementum  in  the 
form  of  fairly  large  bundles.  Upon  emerging  from  the  cementum 
they  break  up  into  smaller  bundles,  bridge  across  the  interspace  and 
are  again  gathered  together  to  be  built  into  the  bone  of  the  alveolar 
process  or  distril)uted  to  support  the  gum.  This  is  the  general  arrange- 
ment. The  direction,  however,  that  these  fibers  take  as  they  pass 
from  their  point  of  origin  in  the  cementum  to  their  insertion  in  the 
bone  or  gum  is  modified  in  various  parts  of  the  membrane  and  is  in 
definite  relation  to  the  force  brought  to  bear  upon  the  tooth  as  it  per- 
forms the  work  of  mastication  and  upon  the  pressure  exerted  against 
the  supported  gum  tissue.  This  adaptation  is  the  more  perfect  in 
that  this  arrangement  is  the  result  of  this  force  and  the  force  not 
secondary  to  the  building  of  the  fibers.  This  is  demonstrated  more 
clearly  perhaps  if  it  is  borne  in  mind  that  the  cement-building  cells 
are  constantly  at  work  shifting  the  attachment  of  fibers  whenever 
there  is  a  change  in  the  direction  of  force  exerted  on  the  tooth.  If  the 
tooth  is  changed  in  position,  the  arrangement  of  the  fibers  of  the  mem- 
brane will  be  varied  to  accommodate  any  changes  in  the  force  of 
mastication. 

For  the  purpose  of  studying  the  arrangement  of  the  principal  fibers, 
the  membrane  may  be  divided  into  three  segments:  (a)  the  gingival, 
that  part  between  the  border  of  the  alveolar  process  and  the  gingival 
margin;  (b)  the  alveolar,  that  part  situated  between  the  border  of 
the  process  and  the  apex;  and  (c)  the  apical,  that  portion  in  relation 
to  the  apex  of  the  root.     (Fig.  39.) 

Arrangement  of  the  Fibers  in  the  Gingival  Portion. — There  are  four 
sets  of  fibers  in  this  area.  The  first  group  arises  from  the  highest  point 
of  attachment  occlusally  on  the  root,  passes  from  this  at  more  or  less 
of  a  right  angle,  then  takes  an  occlusal  curve  and  passes  into  the 
gum  tissue  to  be  lost  among  the  fibers  of  the  connective  tissue  that 
supports  the  epithelium  of  the  mucous  membrane. 

The  second  group  arises  from  an  area  just  below  the  fibers  of  the 
first  group,  passes  out  from  the  cementum  at  right  angles  and  continues 
for  sufficient  distance  into  the  gum  tissue  to  give  this  perfect  support. 
On  the  lingual  side  these  fibers  run  a  longer  course  than  on  the  labial 
because  the  lingual  gum  receives  a  greater  shock  in  chewing  than  does 
the  labial.  The  distribution  of  this  group  of  fibers  on  the  appro.rimal 
side  is  of  extreme  importance.  Here  they  pass  across  the  intervening 
approximal  space  to  the  adjoining  tooth  and  are  built  into  the 
cementum  of  this  tooth.  Each  tooth  receives  and  gives  oft'  fibers  on  the 
aj>jjr()ximal  side  which  are  V>uilt  into  its  cementum.  These,  as  they 
pass  across  the  space,  are  closely  interwoven,  forming  a  basket-work 
structure  that  supports  the  overlying  gum  in  a  most  perfect  manner. 
The  third  (jrovp.  A  little  more  rootward  to  the  second  group  is  another 
set  of  fibers  that  soon  after  passing  from  their  attachment  in  the 
cementum  are  inclined  aj)ically.  These  form  a  very  strong  bundle 
of  fibers.     On  the  labial  and  lingual  sides  they  ])ass  to  the  outer  sur- 


THE  PERIDENTAL  MEMBRANE 


97 


face  of  the  alveolar  process  and  are  attached  to  the  i)eriosteLim  cover- 
ing the  bone  here.     On  the  proximal  side  they  either  pass  to  the 


Fig.  39. — Diagram  of  the  fibers  of  the  perickiital  membrane:  G,  gingival  portion; 
AL,  alveolar  portion;  Ap.,  apical  portion.  (From  a  photograph  of  a  section  from 
incisor  of  sheep.)      (Noyes.) 

cementiim  of  the  adjoining  tooth  or  are  built  into  the  upper  surface 
and  sides  of  the  bone  that  intervenes  between  the  teeth.    These  fibers 

7 


98  SPECIAL  ANATOMY 

resist  any  force  that  tends  to  pull  the  tooth  from  its  socket.  They 
form  what  is  known  as  the  dental  ligament. 

The  fourth  grovp  are  arranged  like  a  constrictor  muscle  around  the 
gingival  margin  and  keep  the  gum  tissue  in  close  contact  with  the 
neck  of  the  tooth. 

Arrangement  in  the  Alveolar  Portion. — Here  are  found  three  areas 
of  variation  in  direction  of  the  fibers.  First:  The  fibers  coming  off 
from  the  cementum  at  the  level  of  the  top  of  the  alveolar  process  pass 
at  right  angles  across  the  intervening  space  to  be  inserted  into  the 
bony  walls  of  the  process.  This  arrangement  is  continued  down  the 
root  of  the  tooth  nearly  one-third  of  the  distance  to  the  apex.  These 
fibers  arise  from  the  cementum  in  strong  bundles  and  then  break  up 
into  fan-like  forms  as  they  cross  the  space  to  be  inserted  into  the  bone. 
In  transverse  sections  of  the  root  at  this  level  it  is  noted  that  the  fibers 
that  come  oft'  from  the  angles  of  the  roots  do  not  pass  immediately 
across  the  space  but  are  deflected  to  right  and  left.  These  are  the 
fibers  that  resist  any  force  that  tends  to  rotate  the  tooth  in  its  socket. 

Second:  As  the  lower  portion  of  the  previously  considered  area  is 
approached  the  fibers,  after  leaving  the  cementum,  begin  to  pass 
occlusally  and  are  inserted  somewhat  higher  up  on  the  wall  of  the 
alveolus.  This  arrangement  is  continued  until  the  apical  end  of  the 
tooth  is  reached.  This  area  is  large  and  the  fibers  are  strong  because 
they  have  to  resist  the  greatest  force  exerted  in  mastication,  /.  e., 
the  thrust  force  as  the  jaws  are  closed.  By  these  fibers  the  tooth 
is  actually  suspended  in  its  alveolus. 

Third:  At  the  lower  portion  of  the  apical  third  of  the  root  the 
fibers  again  begin  to  take  a  more  direct  course  from  the  cementum 
to  the  bone  until  they  are  passing  directly  across,  as  noted  in  the  upper 
third. 

The  Arrangement  in  the  Apical  Portion. — Here  the  fibers  after  passing 
horn  the  cementum  radiate  in  all  directions  before  being  inserted  into 
the  bone.  In  this  way  the  apical  space  is  filled  with  a  mass  of  fibrous 
tissue. 

The  Cells. — Fibroblasts. — These  are  the  cells  that  ha^•e  formed 
the  fibers  and  are  looking  after  their  welfare.  They  are  scattered 
throughout  the  entire  membrane. 

Cementoblasts. — These  are  the  cementum-forming  cells  and  lie  in 
contact  with  this  tissue  between  the  points  of  origin  of  the  fibers. 
As  they  form  the  cementum  some  of  the  cells  surround  themselves 
with  it  and  then  take  the  name  of  cement  cells  or  corpuscles.  They 
also  build  into  the  cementum  the  fibers  of  the  membrane. 

OsteoblasU. — These  are  the  bone-forming  cells  and  have  their  station 
on  the  bony  walls  of  the  alveolus.  They  are  active  in  forming  the  bone 
of  the  alveolar  process  that  is  in  juxtaposition  to  the  roots  of  the 
teeth.  They  too  become  bone  cells  when  they  have  surrouiided 
themselves  with  this  tissue.  The  attachment  of  the  fibers  of  the 
membrane  into  the  bone  is  performed  by  these  elements. 


THE  PERIDENTAL  MEMBRANE  99 

Osteocla.sf.s. — These  are  the  cells  that  eat  away  the  bone  or  cemen- 
tiini  when  there  is  a  demaiul  for  this  j)r()eess.  Through  their  action 
the  fibers  of  the  membrane  are  detached  at  any  o;iven  area.  This 
occurs  during  the  absorption  of  the  roots  of  the  deciduous  teeth  and 
it  is  these  cells  that  are  responsible  for  this  process.  They  are  also 
used  when  nature  believes  that  the  l)one  in  any  given  place  is  too 
thick  and  heavy  for  the  strain  brought  to  bear  upon  it.  If  so,  these 
cells  are  brought  into  activity  and  d(>stroy  the  thick  bone  by  forming 
marrow  spaces  within  it.  This  occurs  in  the  formation  of  the  alveolar 
])rocess  and  accounts  for  its  cancellous  or  spongy  character. 

Bloodvessels. — The  peridental  membrane  has  a  very  rich  supply  of 
blood.  The  arteries  enter  the  apical  space  from  the  bone  beneath. 
They  then  give  off  branches  which  pass  into  the  pulp  cavity  to  supply 
the  organ  therein.  The  main  branches  pass  occlusally  in  all  directions 
through  the  peridental  membrane.  They  lie  nearer  the  wall  of  the 
alveolus  than  the.  cementum.  As  they  pass  upward  they  receive 
from  and  gi\'e  off  })ranches  to  the  bone  of  the  alveolar  wall.  They 
end  by  anastomosing  with  the  bloodvessels  of  the  gum  tissue  and 
help  supply  this  area.  From  this  it  is  noted  that  the  blood  supply 
of  the  gums  and  peridental  membrane  is  intimately  related  so  that 
stimulation  of  gum  tissue  by  massage  and  brushing  will  in  turn  stimu- 
late the  peridental  membrane — a  fact  that  is  of  the  greatest  impor- 
tance in  the  treatment  of  lesions  of  this  latter  structure. 

The  Nerves. — These  have  the  same  point  of  entrance  and  the  same 
distribution  as  the  bloodvessels  that  have  just  been  described.  It  is 
important  to  note  that  these  nerves  give  to  the  peridental  membrane 
the  sense  of  touch.  This  sense  is  well  developed,  for  the  lightest  con- 
tact is  immediately  recognized. 

Epithelial  Elements. — As  the  function  of  these  structures  is  still  a 
mystery  it  is  sufficient  in  this  text  to  note  that  such  tissues  are  present 
but  that  their  real  significance  still  remains  unknown. 

The  function  of  the  peridental  membrane. 

(a)  A  physical  function,  i.  e.,  the  maintaining  of  the  tooth  in  the 
socket. 

(6)  A  vital  function,  manifested  through  the  agency  of  its  cells  in 
the  formation  of  cementum  and  bone. 

(c)  A  sensory  function  in  that  it  supplies  the  sense  of  touch  to  the  tooth . 

Changes  in  the  Membrane  with  Agie. — ^^'hen  the  tooth  first  erupts 
the  sj)ace  between  the  root  and  wall  of  the  alveolus  is  relatively  wide. 
Each  year  finds  this  becoming  smaller  and  smaller  because  of  the 
formation  of  new^  lamellae  of  cementum  on  the  one  side  and  of  bone 
on  the  other.  The  peridental  membrane  grows  proportionately  thinner 
as  it  is  thus  encroached  upon.  However,  there  is  always  membrane 
present  no  matter  what  the  age  of  the  individual  may  be.  In  other 
words,  the  bone  and  cementum  never  come  in  immediate  contact  with 
each  other.  This  thinning  of  the  membrane  makes  it  less  resistant 
to  irritations  and  so  predisposes  inflammatory  conditions.     Hence 


100  SPECIAL  ANATOMY 

diseases  of  the  peridental  membrane  are  more  frequently  found  after 
adolescence. 

The  Alveolar  Process. — As  has  been  perviously  emphasized,  the  bone 
of  this  process  is  built  secondary  to  the  formation  of  the  teeth  or  rather 
coincident  to  their  eruption.  It  is  a  product  of  function  and  is 
arranged  as  to  its  structure  in  a  way  that  will  best  resist  the  forces 
that  are  brought  to  bear  upon  it.  In  the  upper  jaw  we  find  a  dense, 
hard  layer  of  bone  about  the  necks  of  the  teeth  labially  and  buccally. 
In  the  incisor  and  cuspid  region  where  much  force  is  exerted  upon  the 
whole  length  of  the  roots  the  bone  is  quite  thickened  over  their  entire 
labial  surfaces.  This  is  well  demonstrated  in  those  lower  animals  that 
use  these  teeth  for  seizing  and  tearing  their  prey.  0^'er  the  buccal  roots 
of  the  bicuspids  and  molars  it  is  very  thin.  Lingually,  all  the  teeth 
of  the  upper  arch  are  well  supported. 

In  the  lower  arch  again  is  found  the  compact  bone  about  the  necks 
of  the  teeth  and  their  roots  well  supported  buccally,  as  most  of  the 
strain  is  in  this  direction. 

The  great  mass  of  bone  of  both  the  maxilla  and.  the  mandible  is 
made  up  of  the  cancellated  variety  about  the  periphery  of  which  is  a 
layer  of  thick,  dense  bone.  The  wall  of  each  alveolus  joins  this  thick- 
ened layer  at  its  upper  border.  Below  this  point  of  union  the  wall 
of  the  alveolus  is  surrounded  with  cancellated  bone  so  that  the  alveolar 
process  as  a  whole  is  quite  elastic  and  springy.  In  connection  with 
our  reference  to  bony  tissue  it  is  well  to  mention  the  fact  that  this  is 
living  tissue,  a  specialization  of  the  connective  tissues,  adapted  for 
perfect  support  and  that  it  is  ever  throughout  life  undergoing  constant 
change  as  a  result  of  the  mechanical  forces  brought  to  bear  upon  it. 
By  virtue  of  the  ability  to  make  such  changes,  nature  is  able  to  meet 
any  requirement  that  is  demanded,  even  though  it  be  far  different  from 
the  original  condition  for  which  the  bone  was  built.  So  in  examining 
a  specimen  of  bony  tissue  under  the  microscope  various  forms  of  bone 
cell  activity  are  seen  going  on,  representing  different  stages  of  bone 
formation  and  absf)rption. 

Tooth  Formation. — The  first  sign  of  the  formation  of  teeth  is  seen 
in  the  embryo  at  about  two  and  a  half  months.  Along  the  top  of  each 
arch  (upper  and  lower)  there  is  seen  a  heaj:)ing  up  of  the  cells  of  the 
outer  layer  of  tissue.  If  a  cross-section  is  made  of  the  arch,  it  will  be 
noted  tliat  these  cells  are  also  di])])ing  down  into  the  underlying  tissue. 
This  formation  is  known  as  the  dental  rl(l(/e.  From  the  lingual  side 
of  this  ridge  a  shelf-like  growth  is  formed  called  the  lainina.  At 
intervals  along  the  lamina  corresponding  to  location  of  each  tooth 
little  buds  grow  down  from  it.  The  under  surface  of  these  buds 
becomes  indented,  taking  on  the  ap])earance  of  an  inverted  cuj).  This 
structure  is  now  known  as  the  enamel  organ  (Fig.  40),  and  will  soon 
begin  to  lay  down  enamel  along  its  inner  surface.  The  cells  lining  this 
surface  are  the  enamel  cells  and  are  active  in  the  formation  of  this 
substance.    The  enamel  organ  is  of  epithelial  tissue  origin. 


TOO TH  FORMA  TION 


101 


As  the  enamel  organ  is  forming,  the  cells  of  the  tissue  into  which 
it  grows  begin  to  take  on  activities.  As  fast  as  the  infolding  of  the 
base  of  the  enamel  organ  takes  place  the  indentation  is  filled  in  with 
these  active  underlying  tissues  until  a  papilla  is  formed.  This  is  known 
as  the  dental  papilla  (Fig.  40).  This  structure  is  of  connective-tissue 
origin  and  will  become  active  in  the  formation  of  the  dentin.  Growth 
of  the  papilla  continues  until  it  has  assumed  the  shape  of  the  crowni  of 
the  tooth  to  be  formed.  To  this  structure  formed  l^y  the  enamel  organ 
and  dental  papilla  is  given  the  name  of  tooth  germ. 


Fig.  40. — The  enamel  (irjiuii.      The  outer  tunic  connected    i'^    ili.-    lamina  l)y 
the  dental  iiaiiilla  gro\vin<;  up  into  the  cap.    The  spaces  are  shrinkage  spaces. 


t  he   cord ; 
(Noyes.) 


After  the  dental  papilla  has  been  formed  the  cells  at  its  base  develop 
fibrous  tissue  which  grows  up  and  around  the  outer  side  of  the  enamel 
organ  and  over  its  top  so  that  the  tooth  germ  is  enclosed  in  a  fibrous 
sac.  This  combination  of  structures,  /.  e.,  the  fibrous  wall,  the  papilla 
and  the  enamel  organ  constitutes  the  dental  follicle.  This  is  completed 
by  the  end  of  the  twelfth  week. 

Just  before  the  enclosure  takes  place  a  secondary  bud  is  given  off 
from  the  enamel  organ,  usually  near  its  point  of  origin  from  the  lamina, 


102 


SPECIAL  ANATOMY 


which  wpows  downward  to  become  the  enamel  organ  of  the  permanent 
tooth  (Fig.  41). 

Soon  after  the  formation  of  the  dental  follicle  the  bone  of  the  jaw 
below  this  structure  sends  up  processes  which  pass  to  the  lingual  and 
labial  side  of  the  follicle.  Later  bony  growth  appears  on  the  proximal 
sides  and  finally  the  top  is  covered  over.    This  bony  structure  is  what 


Fig.  41. — The  tooth  Korni  showiiiK  the  Imd  for  tlu;  pcrmiiiiciit  tooth  ;it  P.  Calci- 
fimtion  is  just  bcKiniiiiiK:  /'',  folliflc  wiill;  J),  dental  papilhi;  T,  inner  tunic;  7",  outer 
tunic;    .S,  stellatxj  rcticuhitn;   O,  odontol)lasts;    yl,  amelohlasts;    B,  bone.      (Noyes.) 

is  known  as  the  deiifdl  rri/pt  and  simply  serves  as  a  protection  to  the 
forming  tooth.  This  formation  ])ersists  until  the  entire  crown  is 
developed  and  the  tooth  ready  to.  erupt  when  the  top  is  absorbed 
and  the  t(K)th  passes  into  the  mouth. 

At  about  the  sixteenth  week  the  dentin  and  the  enamel  begin  to 
form,  the  former  on  the  outer  edge  of  tlie  dental  pajjilla  and  the  latter 
on  top  of  this  dentin. 


THE  DEVELOPMENT  OF  THE  JAWH  103 

Tlie  roots  of  the  teeth  (h)  not  appear  until  the  tooth  l)egins  to  take 
on  the  process  of  eruption.  At  this  time  also  the  first  of  the  cementum 
is  seen.  This  is  formed  by  cells  in  that  fibrous  tissue  that  grew  up  and 
around  the  enamel  organ  to  complete  the  follicle.  This  fibrous  tissue 
now  may  be  considered  as  the  peridental  membrane.  Coincident 
with  the  formation  of  cementum  by  the  cells  on  the  inner  side  of  this 
membrane  there  is  a  deposit  of  bone  laid  down  by  the  osteoblasts  on 
the  other  side  of  the  membrane.  This  is  the  beginning  of  the  alveolar 
process . 

The  first  permanent  molars  are  the  only  permanent  teeth  for  which 
the  enamel  organ  arises  directly  from  the  lamina.  The  enamel  organs 
for  the  second  and  third  permanent  molars  arise  from  the  buds  of  the 
first  and  second  permanent  molars  respectively. 

THE    DEVELOPMENT    OF    THE    JAWS. 

While  it  is  impossible  in  the  space  alloted  this  subject  to  go  into 
detail  regarding  the  growth  of  the  jaws,  yet  it  is  quite  necessary 
that  the  dental  hygienist  should  know  briefly  the  plan  upon  which 
nature  builds  under  normal  conditions.  For  an  exhaustive  study  of 
this  subject  the  student  is  referred  to  Dr.  Noyes's  text-book,  Dental 
Histology  and  Embryology. 

In  a  comparison  of  the  skull  of  an  infant  at  birth  with  that  of  an 
adult  it  is  noted  that  as  growth  proceeds  there  is  practically  twice 
as  much  development  below  the  nasal  spine  of  the  frontal  bone  as 
above  it.  Passing  in  our  study  to  this  region  of  greatest  change  it 
is  seen  that  in  the  adult  it  can  be  divided  into  thirds,  the  upper  of 
which  is  occupied  by  the  nasal  cavity  and  the  lower  two-thirds  by  the 
organ  of  mastication.  When,  however,  an  attempt  is  made  to  study 
the  child's  head  from  this  point  of  view  it  is  foinid  that  it  is  impos- 
sible to  so  divide  the  head  for  there  is  a  fusion,  as  it  were,  of  the  upper 
two-thirds,  and  that  territory  that  is  entirely  nasal  in  the  adult,  is 
here  more  than  half  given  over  to  the  developing  tissues  of  the  organ 
of  mastication.  To  be  more  specific,  all  that  part  of  the  nasal  cavity 
which  lies  below  the  lower  border  of  the  orbits  is  literally  lined  with 
tooth  germs.  From  this  study  it  may  be  deducted  that  the  great 
(loioncard  growth  in  the  lower  half  of  the  head  is  due  primarily  to  the 
formation  and  subsequent  eruption  of  the  teeth,  and  secondarily  to 
a  continued  growth  of  bone  thrown  out  to  act  as  a  supporting  structure 
for  these  organs.  This  downward  growth  begins  with  the  eruption 
of  the  deciduous  denture  and  continues  until  all  the  permanent  teeth 
anterior  to  the  first  molars  are  in  position.  After  the  completion  of 
the  deciduous  denture  two  new  directions  of  growth  manifest  them- 
selves, a  lateral  or  expanding  grt)wth  to  allow  for  the  difference  in  size 
between  the  teeth  of  the  decidiibus  and  permanent  dentures,  and  a 
forward  one  to  make  room  for  the  developing  permanent  molars.  This 
development  continues  until  all  the  teeth  are  in  position  and  occlusion 
is  established. 


CHAPTER   III. 

PHYSIOLOGY. 

By  ALEXANDER  M.  PRINCE,  M.D. 

Definition. —  General  physiology,  a  branch  of  the  biological  sciences, 
is  concerned  with  the  study  of  function  in  all  living  organisms.  Ilumcm 
physiology,  one  of  its  subdivisions,  deals  with  the  functions  of  the 
body  of  man. 

The  term  function  is  applied  to  all  the  activities  or  life  processes 
of  the  various  parts  of  the  body,  and  in  a  broader  sense  includes  the 
interrelations  of  these  activities  in  the  economy  of  the  individual  as  a 
whole.  As  all  the  reactions  of  the  body  are  dependent  on  physical  and 
chemical  phenomena,  function  may  be  further  defined  as  the  chemistry 
and  physics  of  the  living  body. 

From  the  study  of  anatomy  it  has  been  found  that  the  structural 
unit  of  every  living  thing  is  the  cell  and  that  cells  of  the  same  type  enter 
into  the  formation  of  tissues  which  in  turn  constitute  the  different 
organs.  Likewise,  the  nnit  of  function  is  the  cell,  as  the  behavior  of 
any  tissue  or  organ  depends  upon  the  characteristics  of  its  cells. 

The  Cell. — The  typical  cell  consists  of  a  semifluid,  jelly-like  substance 
called  protoplasm.  This  substance  is  a  complex  chemical  combination 
of  the  following  elements:  nitrogen,  carbon,  oxygen,  hydrogen,  sulphur 
and  a  trace  of  phosphorus. 

The  protoplasm  is  divided  into  the  cytoplasm  which  forms  the  body 
proper  of  the  cell  and  a  spherical  or  oval  body,  usually  found  in  the 
center  of  the  cell,  called  the  nucleus. 

The  maj(jrity  of  cells  contain  but  one  nucleus,  although  not  infre- 
quentl\'  two  or  more  are  present.  In  the  higher  organisms  an  excep- 
tion to  this  rule  is  found  in  the  red  blood  cell,  the  nucleus  of  which  is 
lost  in  the  ])rocess  of  development. 

The  nucleus  is  an  essential  constituent  of  tlic  cell,  for  if  a  cell  is 
divided  })y  section  into  a  luicleated  and  non-nucleated  ])orti()n,  the 
first  regenerates  to  a  complete  cell,  whereas  the  non-nucleated  portion 
soon  dies.  The  formation  of  certain  substances  in  the  cytoplasm  are 
prevented  by  removal  of  the  nucleus  and  furthermore,  reproduction 
cannot  take  ])lace  in  its  absence.  On  the  other  liand,  tiie  nucleus  is 
dependent  on  a  certain  amount  of  cyt()])lasm,  for  if  completely  isolated, 
it  also  perishes.  It  is  therefore  evident  that  both  the  nucleus  and 
cytoplasm  are  essential  to  the  life  processes  of  the  cell. 

Properties  of  Protoplasm. — Protoplasm  is  not  only  very  complex,  })ut 
also  \(Ty  uiisljiblc.     In  the  presence  of  oxygen,  ])r<)toplasm  undergoes 


THE  AMEBA  105 

chemical  changes  with  the  formation  of  simpler  substances.  This 
process  is  known  as  o.vidaiion  and  is  essentially  a  burning  uj)  of  proto- 
plasmic material.  The  result  of  this  combustion  is  the  production  of 
energy  which  manifests  itself  as  heat,  motion,  etc.  The  end-products 
of  oxidation,  which  are  known  as  waste  material.^,  exert  a  poisonous 
influence  on  the  cell  if  allowed  to  accumulate,  but  means  are  available 
for  their  removal  by  the  function  of  excretion.  On  the  other  hand,  the 
waste  resulting  from  the  evolution  of  energy  must  be  constantly 
replaced,  otherwise  death  of  the  cell  would  eventually  follow.  This 
waste  can  only  be  repaired  by  the  absorption  of  new  material  and  it 
is  for  this  reason  that  food  is  required.  The  process  of  breaking  down 
in  the  cell  which  accompanies  the  liberation  of  energy  is  known  as 
vdtdhoJism;  the  repair  and  growth  of  the  cell  is  known  as  anabolism; 
and  these  two  processes  considered  together  are  included  under  the 
term  metabolism. 

Most  foods  as  found  in  nature  are  not  in  a  condition  to  be  absorbed 
and  assimilated  by  the  cell  until  especially  prepared  by  chemical 
processes.  This  function  of  food  preparation  is  present  in  certain 
cells  and  is  known  as  dic/estion.  An  important  function  foimd  in  animal 
life  is  motiJiiy  or  the  ability  to  perform  movements  which  result  from 
changes  in  the  shape  of  the  cell.  This  form  of  cellular  activity  is 
associated  with  the  functif)n  of  irritability,  by  which  the  organism  is 
enabled  to  perceive  and  react  to  external  changes.  As  all  beings 
originate  from  a  preexisting  cell,  the  function  of  reproduction,  which 
permits  such  perpetuation  of  species,  must  be  considered. 

To  recapitulate  then,  it  is  noted  that  there  are  certain  fundamental 
properties  or  functions  common  to  all  forms  of  living  matter:  metab- 
olism, motility,  irritability,  and  reproduction.  These  activities  are 
found  in  a  very  primitive  form  in  single-celled  organisms  and  so  may 
be  advantageously  studied  in  one  of  these,  for  example,  the  ameba. 

The  Ameba. — The  amel)a  is  an  example  of  the  simplest  form  of 
animal  life  and  consists  of  a  single  cell.  It  is  found  in  stagnant  bodies 
of  water  and  moves  about  slowly  by  the  extension  of  finger-like  pro- 
cesses resulting  from  the  flow  of  its  protoplasm.  This  form  of  motility 
is  known  as  ameboid  motion.  This  organism  also  presents  evidence 
of  irritability,  for  it  will  respond  to  external  influences,  moving  toward 
food  particles  and  away  from  harmful  substances. 

This  ameboid  motion  also  serves  as  a  means  of  capturing  particles 
of  animal  and  vegetable  matter  upon  which  it  feeds,  two  protoplasmic 
processes  encircling  the  food  particle  and  forcing  it  into  the  semifluid 
interior  of  the  animal. 

The  food  is  then  slowly  digested  by  juices  formed  in  the  protoplasm 
and  is  distributed  to  all  parts  of  the  cell  where  it  is  utilized  for  repair 
and  the  storage  of  energy  while  the  undigestible  portions  of  the  food 
are  finally  extruded  from  the  cell  body.  These  reactions  represent  the 
functions  of  digestion,  assimilation  and  excretion.  The  ameba  absorbs 
the  oxj'gen  necessary  for  energy  production  from  the  water  in  which 


106  PHYSIOLOGY 

it  lives  and  gives  off  carbon  dioxide.  This  function  is  known  as  res- 
piration. In  this  animal,  reproduction  is  very  simple,  taking  place  by 
division  of  the  nucleus  and  cell  body. 

It  is  noted  from  the  ameba  that  all  functions  may  be  present 
in  one  cell,  but  as  the  scale  of  evolution  is  ascended  animal  forms 
consisting  of  many  cells  are  met  with.  In  these  it  is  found  that  all 
functions  are  not  possessed  alike  by  all  the  cells,  but  that  there  is  a 
dicision  of  labor,  certain  groups  of  cells  becoming  better  adapted  along 
particular  functional  lines.  This  specialization  of  cellular  function 
cannot  be  better  observed  than  in  man,  for  the  human  body  is  essen- 
tially a  large  colony  of  cells  the  individuals  of  which  have  special 
duties  to  perform. 

The  first  physiological  process  that  demands  attention  is  that  of 
nutrition  or  alimentation,  as  it  is  called.  This  is  studied  under  four 
divisions,  /.  e.,  digestion,  absorption,  assimilation,  and  elimination 
or  excretion. 

PHYSIOLOGY   OF   DIGESTION. 

The  human  body  in  the  performance  of  its  functions  is  constantly 
losing  material. 

Every  form  of  activity,  whether  the  contraction  of  a  muscle,  the 
transmission  of  an  impulse  through  a  nerve  or  the  secretory  processes 
of  gland  cells,  is  accompanied  by  catabolic  or  breaking  down  changes 
in  the  cell  protoplasm.  These  changes  result  mainly  from  the  com- 
bination of  oxygen,  carried  in  the  blood,  with  complex  chemical  sub- 
stances in  the  cell.  The  simple  products  arising  from  the  destruction 
of  the  cell  substance,  being  no  longer  of  value  to  the  cell,  are  removed 
by  the  process  of  excretion.  In  order  to  maintain  the  activity  of  the 
tissues,  this  waste  of  substance  must  be  constantly  replaced  by  suit- 
able new  materials,  wliich  are  called  foods. 

Classification  of  Foods. — Foodstuffs  are  divided  into  two  general 
classes:    (I)  nitrogenous  and  (II)  non-nitrogenous. 

I.  The  nitrogenous  foodstuffs  include  the  yroteins  and  the  alhn- 
minoids. 

The  proteins  are  found  in  the  protoplasm  of  all  forms  of  vegetable 
and  animal  life  and  are  chemical  combinations  of  nitrogen,  carbon, 
oxygen,  hydrogen,  sulphur  and  phosphorus.  Protein  has  been  called 
the  "essential"  foodstuff,  as  it  contains  the  necessary  elements  for  the 
repair  of  the  body  cells. 

The  albuminoids,  chemically  allied  to  the  proteins,  are  derived  from 
ccMinective  tissues  (bones,  tendons,  etc.),  but  are  unimportant  as  foods, 
owing  to  the  difficulty  with  which  thej'  are  absorbed  from  the  alimen- 
tary tract. 

II.  The  non-nitrogenous  foodstuff's,  as  the  name  implies,  do  not 
contain  nitrogen  and  include  the  r.drbdlij/drdtrs,  the /a/.v,  the  nrineral 
salts  and  vater. 

The  carbohydrates  consist  of  carbon,  oxygen  and  hydrogen   in  com- 


PHYSIOLOGY  OF  DIGESTION 


107 


bination  ami  are  mainly  derived  from  the  vegetable  world.  This 
division  inclndes  the  starches  and  sugars.  These  substances  are 
readily  oxidized  in  the  body  and  for  that  reason  have  great  energy- 
producing  ])o\ver. 

The  fat.s-  consist  of  the  same  elements  found  in  carl)ohydrates  and 
include  the  oils  and  fats  derived  from  animal  and  plant  life. 

The  most  important  mineral  salts-  required  for  the  needs  of  the  body 
are  the  chlorides,  phosphates,  sulphates  and  carbonates  of  sodium 
and  potassium  and  the  phosphates  and  carbonates  of  lime  and  mag- 
nesium. Of  these  substances  the  chloride  of  sodium  (common  salt) 
is  the  most  essential.  Iron  and  iodin  are  also  necessary  in  small 
quantities. 

]]'(iter  is  a  chemical  compound  of  hydrogen  and  oxygen  and  next 
to  air  is  the  most  important  substance  required  for  the  maintenance 
of  life.  Water  constitutes  70  per  cent,  of  the  body  weight  and  is 
found  in  all  the  tissues  and  fluids  of  the  body.  It  also  acts  as  a  solvent 
for  many  substances  which  could  not  be  otherwise  absorbed  or  excreted. 

TABLE    I.— FOODSTUFFS. 


1.   Nitrogenous 


Proteins 


Albuminoids 


Albumin 

Casein 

Myosin 

Syntonin 

Vitellin 

Gluten 

/  Choiidrin 
\  Gelatin 


Occurrence. 

white  of  eggs,  milk,  blood, 

etc. 
milk  and  cheese. 

muscle  tissue  (meat). 

yolk  of  eggs, 
cereals  (flour). 

cartilage. 

in    bones    and    other    con- 
nective tissue. 


2.  Non-nitrogenous  ■ 


Starches 


Carbohydrates  { 


Sugars 


1  Sucrose 
Glucose 
Maltose 
Lactose 


Fats 


Salts 
[  Water. 


in    all    cereals,     potatoes, 

unripe  fruits, 
sugar  cane, 
fruits, 
malt, 
milk. 


Stearin        1 

Palmitin      I  found  combined  in  animal 

Margarin    f    and  vegetable  fats  and  oil. 

Olein  J 

Lecithin         in  yolk  of  egg  and  nervous 

tissue, 
in    vegetable    and    animal 

tissues  and  directly  from 

mineral  world. 


Most  of  the  foodstuffs  as  they  occur  in  nature  are  not  in  a  condition 
to  be  utilized  by  the  body  cells  until  especially  prepared  by  chemical 
processes.  This  food  preparation  or  digestion  is  accomplished  by 
specialized  cells  associated  with  the  organs  of  the  alimentary  .system. 


lOS  PHYSIOLOGY 

Of  all  the  materials  used  as  foods,  water  and  the  majority  of  the 
salts  are  diffusible  and  therefore  readily  absorbed  by  the  cells  lining 
the  alimentary  canal.  On  the  other  hand,  the  proteids,  carbohydrates 
and  fats  are  not  diffusible,  that  is,  they  will  not  pass  through  an  animal 
membrane  until  their  chemical  nature  has  been  changed.  This  process 
of  making  indiffusible  substances  suitable  for  absorption  is  brought 
about  by  the  action  of  enzymes  secreted  by  the  cells  of  glands  which 
empty  into  the  alimentary  canal. 

Properties  of  Enzymes. — Although  little  is  known  of  the  chemical 
composition  of  enzymes,  these  substances  may  be  recognized  by  the 
folhnving  facts: 

1.  They  are  manufactured  and  secreted  by  living  cells. 

2.  A  very  small  quantity  of  an  enzyme,  without  undergoing  any 
special  change  in  itself,  will  act  upon  enormous  amounts  of  foodstuffs. 

3.  Their  action  is  selective,  that  is,  they  will  only  act  upon  special 
substances,  i.  e.,  ptyalin  only  digests  starches  and  has  no  effect  on 
protein  or  fats. 

4.  Their  action  depends  on  the  reaction  of  the  medium,  i.  e.,  ptyalin 
only  exerts  its  effects  in  alkaline  solutions,  its  chemical  action  being 
arrested  immediately  in  the  presence  of  acids.  Pepsin,  on  the  other 
hand,  acts  in  an  acid  medium. 

5.  Their  activity  depends  on  the  temperature,  being  most  effective 
at  body  temperature,  ceasing  to  act  in  the  cold,  and  being  per- 
manently stopped  at  high  temperatures,  such  as  would  result  from 
boiling. 

Alimentation. — The  alimentary  system  consists  of  a  long  tubular 
channel  running  through  the  body.  Emptying  into  it  at  different  levels 
are  the  ducts  of  the  digestive  glands,  the  cells  of  which  secrete  digestive 
fluids  of  specific  qualities,  some  acting  on  proteins,  others  on  fats  and 
carbohydrates.  Through  the  motility  of  this  alimentary  tube  the  food 
is  propelled  and  progressively  brought  in  contact  with  these  fluids. 
Chemical  transformations  take  place  whereby  the  food  is  prepared 
for  absorption,  the  undigestible  portions  remaining  in  the  digestive 
tract  from  which  they  are  later  expelled. 

Mastication . — The  first  process  of  alimentation  is  mastication  or  the 
chewing  of  food.  The  food  introduced  into  the  mouth  is  ground  by  the 
teeth  and  mixed  with  the  secretion  of  the  salivari/  (/lands.  During  the 
process  of  mastication  the  food  is  finely  reduced  so  that  it  will  oiler  a 
greater  surface  for  the  action  of  the  digestive  juices  and  is  at  the  same 
time  moistened  with  saliva  so  that  it  can  be  more  readily  swallowed. 
Furthermore,  if  any  starches  are  present,  they  are  in  part  transformed 
into  (iilVusible  sugars  by  the  actioji  of  the  salivary  enzymes. 

The  Salivary  Glands. — The  digestive  (/lands  of  the  month  occur  in 
pairs  and  are  named  from  their  location,  the  parotid,  the  sub- 
maxillary and  the  sublingual.  The  secretion  of  these  three  groups 
rtf  glands,  mixed  with  the  mucus  of  microscopic  glands  which  arc 
scattered   throughout  the  mouth,  is  called  salicd. 


PHYSIOLOGY  OF  DIGESTION  109 

P^ach  gland  is  made  up  of  secreting  cells  arranged  in  the  form  of 
small  sacs  which  communicate  l)y  fine  ducts  or  tubules.  These  tubules 
join  to  form  the  larger  ducts  which  open  into  the  mouth.  These  glands 
are  supplied  with  a  rich  network  of  bloodvessels  and  nerves.  Their 
nervous  control  is  beautifully  shown  by  the  marked  secretion  which 
occurs  at  the  sight  or  smell  of  pleasing  foods. 

The  mixed  saliva  of  the  glands  of  the  mouth  consists  in  great  part 
of  water  and  is  of  an  alkaline  reaction.  Among  its  constituents  are 
mucin,  the  substance  which  gives  the  saliva  its  slimy  character  and  an 
enzyme  known  as  yiyalin  to  which  the  partial  digestion  of  starches 
is  due. 

The  food  after  being  thoroughly  masticated  and  mixed  with  saliva 
is  forcetl  into  the  yharyn.v,  a  funnel-shaped  muscular  bag,  by  the 
act  of  deglutition.  By  the  contraction  of  the  pharynx  the  food 
is  then  pressed  into  the  esophagus.  The  latter  structure  is  a  tube 
which  conveys  the  food  from  the  pharynx  to  the  stomach  by  a  pro- 
gressive wave-like  contraction  of  its  muscular  coats.  This  type  of 
muscular  action  which  occurs  also  in  the  stomach  and  intestines  is 
known  as  peristalsis. 

(kistric  Digestion. — The  stomach,  continuous  above  with  the  esophagus 
and  below  with  the  small  intestines,  is  a  muscular  bag  having  a  capac- 
ity of  about  three  pints.  Its  internal  surface  is  lined  with  secreting 
glands  the  cells  of  which  are  arranged  in  the  form  of  simple  tubular 
structures.  The  cells  forming  these  tubules  are  of  three  types;  those 
lying  near  the  opening  of  the  glands  secrete  mucin,  the  other  two 
varieties  secrete  hydrochloric  acid  and  the  enzymes  pepsin  and 
rennin. 

At  the  point  of  junction  with  the  small  intestines  the  stomach  is 
furnished  with  a  muscular  ring  continuous  with  its  muscular  coats. 
This  ring  acts  as  a  valve  and  is  called  the  pyloric  sphincter.  The  junc- 
tion of  this  structure  is  to  prevent  the  further  progression  of  the  food 
until  sufficiently  digested  in  the  stomach. 

The  Gastric  Juice. — The  secretion  of  the  stomach,  known  as  the 
gastric  juice,  is  a  clear,  acid  fluid  consisting  of  water,  hydrochloric 
acid,  to  which  the  acidity  of  this  secretion  is  due,  and  two  important 
enzymes,  pepsin  and  rennin.  These  two  enzymes,  unlike  ptyalin, 
produce  their  effects  only  in  an  acid  medium. 

Pepsin  transforms  the  indiffusible  protein  foodstuff's  into  pep- 
tone. Peptone  differs  from  undigested  protein  by  its  great  solubility 
and  the  ease  with  which  it  passes  through  animal  membranes.  In 
this  way  peptones  are  readily  absorbed  by  the  cells  lining  the  alimen- 
tary canal  and  can  be  then  transferred  to  the  blood  and  carried  away 
to  supply  the  needs  of  nearby  and  distant  cells. 

Rennin  is  an  enzyme  which  acts  on  milk  by  precipitating  the  milk 
protein.  This  protein,  known  as  casein,  is  indift'usible.  After  being 
precipitated  it  is  then  converted  into  peptone  by  the  pepsin. 

The  gastric  juice  does  not  digest  fats  or  carbohydrates,  and  the 


no  PHYSIOLOGY 

digestion  of  starches  previously  begun  in  the  mouth  is  soon  arrested 
by  the  acid  reaction  of  the  gastric  secretion. 

The  stomach  by  the  contraction  of  its  muscular  walls,  churns  the 
food  so  that  it  is  thoroughly  mixed  with  the  secretions,  thus  hastening 
the  process  of  digestion.  The  food,  when  gastric  digestion  is  com- 
pleted, is  reduced  to  a  grayish  liquid  material  known  as  chyme.  At 
this  stage  the  pyloric  sphincter  relaxes  and  allows  the  gradual  passage 
of  the  stomach  contents  into  the  small  intestines. 

Although  the  stomach  is  richly  supplied  with  bloodvessels,  only  a 
very  small  portion  of  the  digested  foods  are  absorbed  into  the  blood 
from  this  organ,  so  that  the  stomach,  like  the  mouth,  is  concerned 
principally  with  the  preliminary  preparation  of  food. 

The  Squall  Intestine. — Th  esmall  intestine,  where  final  digestion  and 
absorption  take  place,  is  a  muscular  tube,  the  mucous  membrane  of 
which  is  thrown  into  folds  so  as  to  offer  a  greater  surface  for  absorp- 
tion. This  mucous  membrane  consists  largely  of  finger-like  projections 
called  I'iUi,  between  which  lie  tubular  glands  (glands  of  Lieberkiihn) 
which  produce  a  secretion  known  as  the  succus  entericus.  This  secre- 
tion contains  water,  mucin  and  some  enzymes  concerned  with  the 
digestion  of  protein  and  the  transformation  of  indiffusible  carbo- 
hydrates into  dextrose. 

In  the  upper  part  of  the  small  intestine  (the  duodenum)  open  the 
ducts  of  two  large  glands,  the  liver  and  the  ixincreas. 

The  Liver. — The  liver  is  a  large  gland  which  secretes  an  alkaline, 
golden-yellow  fluid  known  as  hile.  The  principal  junction  of  the  bile 
is  to  neutralize  by  its  alkalinity  the  acid  chyme  derived  from  gastric 
digestion,  and  thus  prepare  it  for  the  action  of  the  pancreatic  enzymes 
which  are  effective  only  in  an  alkaline  medium.  The  bile  t:'ontains 
pigments  and  salts.  The  hile  salts  are  especially  important,  as  they 
aid  in  the  digestion  and  absorption  of  fats  in  the  presence  of  the 
pancreatic  secretion. 

The  Pancreas. — The  pancreas  is  a  gland  much  larger  but  similar  in 
structure  to  the  salivary  glands.  Its  cells  secrete  an  alkaline  fluid 
which  contains  three  important  enzymes,  trypsin,  amylopsin  and 
steapsin. 

Trypsin  has  an  action  similar  to  pepsin,  as  it  transforms  proteins 
into  peptones,  but  in  this  case  only  in  an  alkaline  medium. 

Amylopsin  is  similar  in  its  action  to  ptyalin,  transforming  starches 
into  sugar. 

Steapsin  is  the  enzyme  concerned  with  the  digestion  of  fats.  Under 
its  influence  fats  are  broken  up  into  glycerin  and  fatty  acids.  Glycerin 
is  readily  absorbed  by  the  intestinal  cells  and  the  fatty  acids  combine 
with  the  alkali  of  the  pancreatic  juice  and  bile  to  form  soaps  which 
are  very  diffusible.  The  rest  of  the  fats  which  are  not  changed  in  this 
manner  are  emulsified  or  reduced  to  fine  division  by  the  action  of  the 
soaps.  The  fat  emulsioi)  and  soaps  arc  then  in  a  form  which  can  be 
absorbed  bv  the  vilH. 


I'llYSIOUmV  OF   ABSORPTION 


111 


As  ill  the  stomach,  the  food  is  kept  in  motion  1)\'  the  peristalsis  of 
the  intestines  so  that  finally  the  food  is  distril)nted  throvij^hout  the 
small  intestine  for  (ihsorj/tion.  The  contents  of  the  small  intestine 
when  digestion  is  complete  are  known  as  chyle  and  have  a  creamy 
color  owing  to  the  presence  of  finely  divided  fat. 

The  original  food  which  was  taken  into  the  mouth  as  nnabsorbable 
proteins,  carbohydrates,  and  fats  is  now  converted  into  peptone,  sugar, 
glycerin,  soaps  and  emulsified  fats,  any  one  of  which  can  readily  be 
absorbed. 

TABLE    II.— DIGESTION    IN   THE   ALIMENTARY   CANAL. 


Place. 


Secretion. 


Source. 


Enzyme. 


Reaction  of 
medium. 


Foods  acted 
upon. 


Final 
products. 


A.  Mouth       Saliva 


li.  Stomach    Gastric 
juice 


C.  Small 
intestines 


Secreting   cells    Ptyalin 

of      salivary 

glands 
Peptic  glands      Pepsin 


Rennin 


Pancreatic 
juice 


Bile 


Succus   en- 
entericus 


Pancreatic 
cells 


Liver  cells 


Intestinal 
gland  cells 


Alkaline 


Acid 


Trypsin 

Amylopsin 

Steapsin 

None 
Maltase 


Acid 


Alkaline 
Alkaline 
Alkaline 


Alkaline 
Alkaline 


Starches 


Proteins 
Milk 


Proteins 

Starches, 

sugars 

Fats,  oils 


Aids  pan- 
creas in  fat 
digestion. 

IndSfusible 
sugars 


Dextrin,  mal- 
tose. 

Peptones. 

Casein  precipi- 
tated (milk 
curds)  which 
pepsin  trans- 
forms into 
peptone. 

Peptones. 

Maltose. 

Fatty        acids, 
glycerin 
(emulsified 
fats,   soaps). 


Dextrose. 


PHYSIOLOGY    OF    ABSORPTION. 

Practically  all  ah.sorpfioti  takes  place  in  the  small  intestine.  This 
proceeds  in  two  different  ways.  (1)  Absorption  into  the  lymphatics 
by  means  of  the  villi,  and  (2)  direct  absorption  into  bloodvessels, 
tributaries  of  the  portal  circulation. 

Fats  are  absorbed  by  the  lymphatics;  sugars,  peptones,  salts,  etc., 
by  the  bloodvessels. 

The  villi  are  small  finger-like  structures  containing  a  lymphatic 
channel  surrounded  by  a  network  of  fine  bloodvessels,  the  whole 
being  covered  by  a  single  layer  of  columnar  shaped  cells.  These  lym- 
phatic channels  or  lacteals  of  the  villi  connect  with  larger  lymphatic 
vessels  which  eventually  empty  into  the  general  circulation  by  means 
of  a  large  lymphatic  vessel  known  as  the  thoracic  duct. 

Fats  are  absorbed  by  the  cells  lining  the  villi  and  passed  into  the 
central  lymphatic  channels.  They  are  then  carried  through  this  system 
of  vessels  and  thrown  directly  into  the  blood  stream  to  be  distributed 
to  all  parts  of  the  body. 

The  intestinal  tract  is  furnished  with  a  rich  network  of  fine  blood- 
vessels which  lies  directly  under  the  cells  lining  the  intestines.    The 


112  PHYSIOLOGY 

bloodvessels  or  capillaries  forming  this  network  fuse  into  larger  vessels 
which  empty  into  the  liver  by  means  of  a  large  vein  called  the  portal. 
Peptones,  sugars,  salts  and  icater  pass  into  these  bloodvessels  and 
hence  are  taken  through  the  liver  before  their  final  distribution  to 
the  body  cells. 

PHYSIOLOGY   OF   ASSIMILATION. 

Peptones,  after  undergoing  further  changes  in- the  liver,  are  dis- 
tributed to  all  the  cells  by  the  general  circulation  and  there  are  used 
for  the  repair  of  the  cell  protoplasm. 

The  sugar  (dextrose)  in  excess  of  the  immediate  requirements  of 
the  body,  is  stored  in  the  liver  cells  as  glycogen.  This  substance  is 
an  insoluble  sugar  formed  from  dextrose  by  the  liver  cells  with  the 
aid  of  an  internal  secretion  furnished  by  the  pancreas.  This  glycogen 
is  retained  in  the  liver  until  called  for  by  the  tissues  when  it  is 
reconverted  into  dextrose  and  carried  away  by  the  blood  stream. 

If  carbohydrates  are  taken  in  excess,  so  that  the  limit  of  storage 
is  reached  in  the  liver,  sugar  is  converted  by  connective-tissue  cells 
into  fat  which  is  stored  in  various  parts  of  the  body,  under  the  skin, 
about  the  mesenterj^  etc. 

Fats  are  utilized  like  sugar  in  the  production  of  energy,  work,  animal 
heat,  etc.,  and  if  in  excess  are  also  stored  as  fats  for  future  use. 

The  Removal  of  Waste  Products. — By  the  peristalsis  of  the  small 
intestine  the  undigestible  portions  of  the  food  are  gradually  carried 
to  the  large  intestine.  The  contents  of  the  latter  structure  are 
practically  free  from  absorbable  substances.  This  undigested  food 
undergoes  bacterial  changes,  becoming  acid  in  the  process,  while 
the  large  amount  of  water  present  is  removed  by  absorption.  It 
is  then  known  as  the  feces  and  as  such  is  finally  expelled  from  the 
body. 

The  physiology  of  elimmation  or  excretion  is  considered  in  detail 
on  page  122. 

THE   PHYSIOLOGY    OF    RESPIRATION. 

Chemical  Changes. — When  oxygen  combines  chemically  with  carbon  a 
gaseous  compound  is  formed  known  as  carbon  dioxide.  This  chemical 
reacticni  (oxidation)  is  always  accompanied  by  the  liberation  of  energy 
which  appears  as  heat.  By  suitable  means  heat  may  be  converted  into 
some  other  form  of  energy,  for  instance,  mechanical  work. 

These  changes  are  well  illustrated  by  the  steam  engine  in  which 
coal,  a  substance  rich  in  carbon,  coml)iiics  with  the  atmospheric  oxygen 
to  form  carbon  dioxide,  the  result  of  this  oxidation  being  to  liberate 
energy  in  the  form  of  heat.  This  heat  applied  to  the  boiler  converts 
the  water  it  contains  into  steam,  and  the  pressure  of  the  latter  is  then 
transferred  to  the  functionating  parts:    piston,  piston  rod,  wheel,  etc., 


THE  PHYSIOLOGY  OF  RESPIRATION  113 

so  that  the  energy  derived  from  a  chemical  process,  the  l)uniing  of 
coal,  is  transformed  into  mechanical  work. 

In  the  living  cell  are  fonnd  similar  processes  occurring  in  a  modified 
form.  In  fact  every  cell  is  a  minute  chemical  engine,  burning  fuel  and 
liberating  energy.  In  the  cell  the  fuel  consists  of  carbonaceous 
materials  in  the  protoplasm  which  have  been  derived  from  the  carbo- 
hydrate, fat  and  protein  foodstuffs. 

This  carbon-rich  material  combines  with  oxygen  absorbed  from  the 
surrounding  medium  of  the  cell  and  carbon  dioxide  is  formed.  This 
chemical  reaction,  as  in  the  steam  engine,  is  associated  with  the  evolu- 
tion of  energy  which  appears  as  heat  (animal  heat)  and  work,  the 
latter  manifesting  itself  in  different  forms  of  activity  according  to  the 
structure  and  the  functional  capacity  of  the  cell. 

Although  many  other  chemical  activities  occur  in  living  cells, 
oxidation  is  by  far  the  most  important  of  these.  Deprived  of  oxygen, 
cells  soon  lose  their  functionating  powers,  and  as  life  is  absolutely 
dependent  on  the  proper  maintenance  of  functions,  it  is  evident  that 
oxygen  must  be  constantly  supplied  to  all  the  body  cells. 

Carbon  dioxide,  the  final  product  of  oxidation,  is  no  longer  of 
value  to  the  cell,  and  like  all  excretory  products  acts  as  a  poison  if 
allowed  to  accumulate  in  the  medium  in  which  cells  live.  Therefore 
some  means  must  also  be  available  to  remove  carbon  dioxide  as  rapidly 
as  it  is  formed. 

The  function  through  which  oxygen  is  supplied  to  the  tissues  and 
carbon  dioxide  removed  is  known  as  respiration. 

In  a  single-celled  organism,  such  as  the  ameba,  no  special  organs 
are  required  for  this  interchange  of  gases.  Oxygen  is  derived  from 
the  water  in  which  this  animal  lives  by  direct  absori)tion  into  the 
cell  and  carbon  dioxide  is  excreted  into  the  same  medium. 

In  higher  animals  the  same  processes  take  place,  for  the  body  cells, 
like  the  ameba,  live  in  a  fluid  medium  which  is  represented  by  the 
blood  and  l>Tnph.  Each  cell  obtains  its  oxygen  from  the  circulating 
blood  and  the  carbon  dioxide  is  excreted  in  these  body  fluids.  But 
the  blood  must  carry  a  constant  supply  of  oxygen  and  at  the  same 
time  some  provision  must  be  made  to  remove  the  carbon  dioxide 
which  would  otherwise  accumulate  and  exert  a  noxious  influence  on 
the  tissues.  This  is  accomplished  in  higher  forms  of  life  through  the 
agency  of  the  lungs. 

The  air  is  a  mixture  of  three  gases,  oxygen,  nitrogen  and  carbon 
dioxide.  During  the  process  of  respiration  this  air  is  drawn  into  the 
lungs  where,  owing  to  the  structure  of  these  organs,  the  gases  are 
brought  into  intimate  contact  with  the  circulating  blood. 

It  will  be  seen  under  the  pliA'siology  of  the  circulation  that  the 
blood,  after  having  been  in  contact  with  the  tissues,  is  carried  to  the 
lungs.  There  the  carbon  dioxide  formed  by  oxidation  in  the  cells 
is  thrown  off  and  a  new  supply  of  oxygen  is  absorbed  by  the  blood  to 
replace  that  part  of  the  oxygen  which  has  been  utilized  by  the  body 


114  PHYSIOLOGY 

cells.  After  this  interchange  the  now  purified  blood. leaves  the  lungs 
to  be  redistributed  throughout  the  body. 

The  air  in  the  lungs  must  also  be  changed  at  frequent  intervals, 
otherwise  there  would  be  an  insufficient  supply  of  oxygen  for  the  blood 
to  absorb  while  the  carbon  dioxide  in  the  blood  could  not  be  eliminated. 
It  is  for  this  purpose  that  nature  provides  the  respiratory  act,  which 
is  simply  an  alternate  inflation  and  deflation  of  the  lungs,  by  virtue 
of  which  the  air  in  these  organs  is  constantly  renewed.  Respiration 
is  therefore  divided  into  two  phases:  inspiration,  during  which  the 
external  air  is  drawn  into  the  lungs;  and  expiration,  during  which  air, 
now  deficient  in  oxygen  and  laden  with  carbon  dioxide,  is  expelled. 

The  Respiratory  System. — In  man  the  organs  of  respiration  are  classi- 
fied for  description  as  follows:  (1)  The  respiratory  passages,  a  system 
of  cavities  and  tubes  through  w^hich  the  atmospheric  air  gains  access 
to  the  lungs  and  through  which  the  impure  air  is  expelled.  (2)  The 
lungs,  where  the  interchange  of  gases  of  the  air  and  blood  takes  place. 
(3)  The  thorax,  which  by  its  expansion  fills  the  lungs  with  a  fresh 
supply  of  air  and  which  by  its  relaxation  aids  in  the  expulsion  of  the 
impure  air.  (The  latter  function  is  effected  principally  through  the 
collapse  of  the  lungs  by  virtue  of  their  elasticity.)  (4)  Nervous 
structures,  which  control  the  rate  and  depth  of  respiration. 

Air  may  pass  into  the  respiratory  passages  by  way  of  the  nose  or 
mouth.  Of  these  two  the  nasal  passages  are  especially  adapted  for 
breathing,  for  the  ca\ity  of  the  nose  is  lined  with  mucous  membrane 
richly  supplied  with  bloodvessels  which  aid  in  warming  the  inspired 
air;  furthermore,  this  membrane  is  thrown  into  intricate  folds  so  that 
much  of  the  dust  and  other  impurities  of  the  air  which  would  other- 
wise enter  the  respiratory  passages  do  not  pass  beyond  the  nasal  cavity. 
The  mouth  and  nose  communicate  with  the  pharynx  and  the  latter 
with  the  larynx.  • 

The  larynx  is  a  cartilaginous  box,  triangular  on  cross-section  above 
and  circular  below  where  it  is  continuous  with  the  trachea.  Like  all 
the  respiratory  passages,  it  is  lined  with  mucous  membrane.  In  the 
triangular  portion  of  the  larynx,  the  vocal  cords  are  situated.  These 
structures  are  bands  of  elastic  tissue,  lying  directly  under  the  mucous 
membrane,  which  by  their  vibration,  under  the  influence  -of  a  blast  of 
air,  produce  sounds  known  as  the  voice. 

At  the  upper  extremity  of  the  larynx  and  lying  just  behind  the 
tongue  is  a  leaf-shaped  structure,  the  epiglottis,  consisting  of  cartilages. 
Although  not  directly  associated  with  the  respiratory  act,  the  epi- 
glottis is  of  great  importance,  as  by  its  lid-like  action  it  closes  the 
larynx  during  swallowing  and  thus  prevents  the  passage  of  food  into 
the  respiratory  tract. 

The  trachea  is  continuous  above  with  the  larynx.  The  mucous  mem- 
brane of  this  tube  anrl  its  subdivisions  is  of  special  interest,  as  the 
uppermost  layer  of  this  incmljraiic  consists  of  ciliated  cells.  These 
cells  are  furnished  with  cilia,  or  hair-like  processes  which  l)y  their 


THE   I'ilY Slower  OF   UESl'l RATION  115 

motility  swcej)  dust  i)artides  toward  the  external  world  and  thus 
prevent  theii"  entrance  into  the  lungs. 

The  sul)di^•isions  of  the  trachea,  the  bronchi  and  bronchioles,  are 
generally  included  with  the  lungs.  The  two  bronchi,  into  which  the 
trachea  divides,  enter  the  right  and  left  lungs  respectively,  where 
they  subdivide  into  numerous  smaller  tubes  known  as  the  bronchioles. 
(The  l)r()nchi  and  the  larger  bronchioles  are  similar  to  the  trachea  in 
structure,  but  the  smaller  bronchioles,  those  which  terminate  in  the 
air  chambers  of  the  lungs,  have  much  thinner  walls  and  are  not  sup- 
plied with  cartilaginous  rings.)  The  bronchioles  further  subdivide 
and  finally  terminate  in  dilated  cavities,  the  infundibula.  The  walls  of 
each  infundibulum  are  closely  beset  with  still  smaller  chambers,  the 
alveoli,  where  the  actual  exchange  of  gases  takes  place.  The  alveoli 
consist  of  a  single  layer  of  flat  cells  supported  by  delicate  elastic  tissue 
under  which  lie  a  close  network  of  capillaries  (small  bloodvessels).^ 

The  lungs  therefore  consist  of  myriads  of  these  air  chambers,  fur- 
nished with  passages  (bronchioles  and  bronchi)  leading  to  the  external 
air. 

The  lungs  are  enclosed  in  a  conical  shaped,  air-tight  chamber 
known  as  the  thorax.  Each  lung  is  tucked  into  a  sac,  the  pleura,  one 
layer  of  which  invests  the  surface  of  the  lung,  the  other  being  attached 
to  the  inner  surface  of  the  thorax.  This  sac  is  lined  with  a  single 
layer  of  flat  cells  which  secrete  a  thin  fluid.  The  purpose  of  this  secre- 
tion is  to  reduce  the  friction  between  the  limgs  and  the  thorax  during 
respiration. 

The  bones  of  the  thorax  are  the  sternum  in  front,  the  twelve  ribs  on 
each  side  and  the  thoracic  vertebrae  behind.  Owing  to  the  convexity 
of  the  ribs  and  the  peculiar  manner  in  which  they  articulate  with  the 
vertebrae,  the  capacity  of  the  chest  is  greatly  increased  when  the  ribs 
are  elevated  by  the  contraction  of  muscles  during  inspiration.  Run- 
ning obliquely  between  the  adjacent  ribs  are  tw^o  sets  of  muscles,  the 
internal  and  external  intercostals.  The  base  of  the  thorax  is  shut  oft' 
from  the  abdominal  cavity  by  the  diaphragm,  a  dome-shaped  muscle 
with  its  convexity  upward.  The  structures  at  the  root  of  the  neck 
complete  the  thorax  above. 

The  muscles  concerned  in  respiration  are  activated  by  impulses 
transmitted  through  nerves,  which  in  turn  are  controlled  by  a  central 
station  known  as  the  respiratory  center. 

The  respiratory  center  is  composed  of  nerve  cells  situated  in  the 
medulla  (a  portion  of  the  central  nervous  system  lying  between  the 
upper  part  of  the  spinal  cord  and  the  brain).  These  cells  are  sur- 
rounded by  bloodvessels  and  react  to  changes  in  the  gaseous  contents 
of  the  blood,  being  especially  susceptible  to  increases  in  carbon  dioxide. 

^  It  will  be  noted  that  the  air  contained  in  the  alveoli  is  separated  from  the  circulating 
blood,  by  only  two  layers  of  flat  cells,  one  layer  forming  the  wall  of  the  alveolus,  the 
other  the  wall  of  the  capillarJ^  Through  this  double  membrane  oxygen  and  carbon 
dioxide  can  diffuse  with  great  facility. 


116  PHYSIOLOGY 

The  Mechanics  of  Respiration. — During  inspiration  the  muscles  of  the 
thorax  contract  under  the  influence  of  impulses  sent  through  nerves 
from  the  respiratory  center. 

The  int-ercostal  muscles  (the  external  and  internal)  by  their 
contraction  lift  the  ribs  and  increase  the  lateral  and  anteroposterior 
diameters  of  the  chest.  At  the  same  time  the  diaphragm  contracts 
and  thus  becomes  flatter,  its  central  portion  moving  downward,  so 
that  by  the  simultaneous  contraction  of  these  muscles  the  capacity 
of  the  thorax  is  increased  in  all  dimensions. 

This  enlargement  of  the  thorax  must  be  followed  by  an  expansion 
of  the  lungs  as  the  pressure  exerted  through  the  respiratory  passages 
(atmospheric  pressure)  upon  the  interior  of  the  alveoli  is  always  greater 
than  the  counter-pressure  exerted  by  the  elasticity  of  the  lungs.  As 
the  lungs  expand  the  pressure  in  the  alveoli  necessarily  becomes  less 
than  that  of  the  external  air  so  that  the  latter  rushes  into  the  alveoli 
until  an  equilibrium  is  established.  It  is  during  this  phase,  known  as 
inspiration,  that  a  fresh  supply  of  oxygen  is  brought  in  contact  with 
the  blood  circulating  in  the  lung. 

The  lung  tissue  is  also  supplied  with  nerves  and  the  expansion  of 
the  lungs  gives  rise  to  nervous  impulses,  which  reaching  the  respiratory 
center,  arrest  the  impulses  to  the  respiratory  muscles,  so  that  the 
latter  relax.  With  this  relaxation  expiration  sets  in.  The  ribs  are 
brought  back  to  their  position  of  rest  by  gravitation  and  by  virtue  of 
the  elasticity  of  the  thoracic  cage.  Furthermore,  the  return  to  the 
expiratory  position  is  aided  by  the  traction  exerted  upon  the  chest 
walls  by  the  elasticity  of  the  lungs. 

As  the  capacity  of  the  thorax  and  consequently  the  volume  of  the 
lungs  diminish  the  pressure  in  the  alveoli  becomes  greater  than  that 
of  the  external  air,  so  that  the  lung  air,  deficient  in  oxygen  and  rich 
in  carbon  dioxide,  is  expelled  through  the  respiratory  passages. 

Changes  in  the  Air. — Atrnospheric  air  contains  21  per  cent,  of  oxygen, 
79  per  cent,  of  nitrogen  and  a  small  fraction  of  carbon  dioxide  (3  parts 
in  10,000).  The  expired  air,  on  the  other  hand,  contains  about  17  per 
cent,  of  oxygen,  79  per  cent,  of  nitrogen  and  4  per  cent,  of  carbon 
di(jxide.  This,  of  course,  indicates  that  during  respiration  about  4 
per  cent,  of  oxygen  is  absorbed  by  the  blood  and  4  per  cent,  of 
carbon  dioxide  excreted  from  the  blocxl  into  the  alveoli.  The  nitrogen 
percentage  remains  the  same,  for  it  l)ehaves  as  a  neutral  gas  and  is  not 
absorbed  in  the  lungs.  It  should  also  be  mentioned  that  the  blood  in 
passing  through  the  lungs  gives  oft'  a  small  amount  of  its  water,  about 
one  pint  being  excreted  daily. 

The  raie  and  dejjfli  of  respiration  vary  with  the  age  and  the  degree 
of  activity  in  the  iiirlivi(hial.  In  the  adult  the  normal  rate  during 
re.st  is  about  Ki  to  20  jjcr  miimte  and  the  amount  of  air  taken  in  each 
inspiration  is  about  1  pint.  Both  the  rate  and  depth  of  respiration 
increase  markedly  during  exercise,  the  total  capacity  of  the  lungs 
under  forced  breathing  being  about  seven  pints. 


PHYSIOLOGY  OF   THE  CIRCULATION  117 

Nervous  Mechanism. — At  first  sight  the  respiratory  act  appears  to 
l)e  under  control  of  tlic  will,  hut  this  is  true  only  to  a  slight  degree. 
Resi)iration  is  actually  an  involuntary  function  under  the  constant 
regulation  of  the  respiratory  center.  As  has  been  seen,  the  irritability 
of  this  center  is  influenced  by  the  carbon  dioxide  contents  of  the  blood. 
Durimj  exercise  when  the  activity  of  the  muscles  gives  rise  to  an  in- 
crease of  carbon  dioxide  in  the  circulating  blood,  the  respiratory  center, 
which  is  sensitive  to  slight  changes  of  carbon  dioxide,  is  stimulated  to 
greater  activity.  This  stimulation  of  the  center  is  followed  by  a  cor- 
responding increase  of  activity  in  the  respiratory  muscles,  so  that 
respiration  during  exercise  is  deeper  and  more  rapid.  Conversely, 
during  sleep  less  carbon  dioxide  is  formed  in  the  tissues,  the  respira- 
tory center  is  not  so  strongly  stimulated  and  consequently  respiration 
is  consideral)ly  slower. 

'^rhere  is,  therefore,  in  the  respiratory  function,  not  only  a  means 
of  supplying  the  tissues  with  oxygen  and  removing  carbon  dioxide, 
but  also  an  automatic  mechanism  whereby  the  supply  and  removal 
is  controlled  according  to  the  constantly  changing  requirements  of 
the  body. 

PHYSIOLOGY    OF    THE    CIRCULATION. 

The  Circulatory  System, — The  circulatory  organs  consist  essentially 
of  a  closed,  continuous  system  of  tubes  through  which  blood,  the 
common  nutritive  fluid  of  the  body,  is  kept  in  constant  circulation 
b}'  the  pump-like  action  of  the  heart. 

The  circulating  blood  serves  two  'purposes:  to  convey  food  and 
oxygen  to  the  body  cells  and  to  carry  to  the  organs  of  excretion  the 
waste  products  resulting  from  cellular  activity. 

The  Blood. — The  blood  is  a  red,  opaque  fluid  and  makes  up  about 
one-thirteenth  of  the  body  weight.  On  microscopic  examination  this 
fluid  is  found  to  consist  of  several  varieties  of  cells  suspended  in  a 
clear  yellowish  fluid  known  as  plasma. 

The  cellular  elements  of  the  blood  are  of  three  types:  the  red  blood 
cells  or  erythrocytes,  the  white  blood  cells  or  leukoc^'tes  and  the  blood 
platelets. 

The  red  blood  cells  are  thin,  biconcave,  non-nucleated,  circular  disks, 
about  one  thirty-five  hundredths  of  an  inch  in  diameter.  These  cells 
are  composed  of  protoplasm  in  which  is  found  an  iron-containing  sub- 
stance called  hemoglobin.  It  is  to  this  substance  that  the  red  color 
of  the  blood  is  due.  Hemoglobin  has  a  great  affinity  for  oxygen,  and 
owing  to  this  property  the  red  blood  cells  are  able  to  absorb  oxygen 
during  their  passage  through  the  lungs. 

The  white  blood  cells  or  leukocytes,  less  numerous  and  somewhat 
larger  than  the  red  blood  cells,  are  more  or  less  irregular  in  shape, 
colorless,  and  have  a  well-defined  nucleus.  By  a  form  of  motility 
similar  to  that  of  the  ameba  (ameboid  motion)  these  cells  are  able 
to  engulf  foreign  particles.     This  function,  known  as  phagocytosis,  is 


118  PHYSIOLOGY 

especially  important  in  disease,  the  invading  germs  being  destroyed 
in  great  numbers  by  the  leukocytes.  Another  property  of  the  white 
blood  cells  is  the  production  of  a  ferment  which  assists  in  the  clotting 
of  blood. 

The  bJood  platelets  are  very  small  cells  probably  concerned  only  with 
the  process  of  clotting. 

The  fluid  portion  of  the  blood  or  plasma  is  a  yellowish,  alkaline 
fluid  consisting  of  90  parts  of  water  holding  in  solution  albumin,  sugar, 
mineral  salts,  and  other  substances  which  are  constantly  replenished 
by  the  intake  of  food.  The  plasma  therefore  represents  the  nutritive 
element  of  the  blood  from  which  the  cells  derive  their  needs.  Owing 
to  the  alkalinity  of  the  plasma,  carbon  dioxide  is  readily  dissolved  in 
this  fluid,  and  in  this  manner  is  carried  from  the  cells  to  the  lungs  where 
this  gas  is  excreted.  The  plasma  also  acts  as  a  solvent  for  other 
excretor}'  products  of  the  cells  which  can  be  then  conveyed  to  the 
excretory  organs  and  there  finally  expelled  from  the  body. 

The  blood  when  removed  from  the  body  is  soon  transformed  into 
a  semisolid  mass.  This  transformation,  known  as  coagulation  or 
clotting,  takes  place  through  the  agency  of  a  ferment  derived  from  the 
blood  platelets  and  leukocytes. 

This  ferment  precipitates  part  of  the  albumin  of  the  plasma  in  the 
form  of  delicate  fibrils  which  form  an  interlacing  network.  In  this 
network  the  cellular  elements  become  entangled,  the  whole  mass  form- 
ing the  clot.  The  purpose  of  coagulation  is  to  prevent  the  excessive 
loss  of  blood  after  injury  to  the  tissues,  the  coagulated  mass  occluding 
the  mouths  of  the  bleeding  vessels. 

The  blood  is  kept  in  constant  circulation  throughout  the  body  by 
the  pumping  action  of  the  heart. 

The  Heart. — The  heart  is  a  hollow  muscular  organ,  conical  in  shape. 
It  is  situated  in  the  thorax,  lying  between  the  two  lungs  just  above 
the  diaphragm  and  behind  the  breast-bone  or  sternum.  It  is  placed 
obliquely  so  that  its  apex  reaches  to  a  point  just  inside  and  a  little 
below  the  left  nipple.  The  heart  is  surrounded  by  the  pericardium,  a 
connective-tissue  pouch  made  up  of  two  layers,  one  of  which  is  closely 
adherent  to  the  heart  wall,  the  other  being  attached  to  the  surround- 
ing structures.  The  interior  of  this  pouch  is  lined  with  a  single  layer 
of  flat  cells  which  secrete  a  thin  fluid.  This  fluid  serves  to  diminish 
the  friction  between  the  heart  and  the  adjacent  organs. 

The  interior  of  the  heart  is  divided  by  a  longitudinal  muscular  wall 
into  two  distinct  cavities,  each  of  these  cavities  being  subdivided  by 
valves  into  two  compartments,  a  lower  and  an  upper,  which  com- 
municate with  each  other.  The  heart  is  thus  divided  into  four 
chambers.  "^I'he  two  upi)er  chambers  are  called  the  right  and  left 
auricles,  the  two  lower,  the  right  and  left  ventricles.  The  outlets  of 
these  cham})ers  are  guarded  by  valves  which  prevent  the  back  flow  of 
l)lood  after  its  expulsion  from  any  one  fhamber  and  keeps  the  })lood 
circulating  in  the  same  direction. 


PHYSIOLOGY  OF   THE  CIRCULATION  119 

The  heart  walls  consist  of  muscle  cells,  roughly  columnar  in  shape 
and  striated.  These  cells  have  the  peculiar  property  of  contracting 
and  relaxing  at  fairly  definite  intervals.  This  rythmical  action  gives 
rise  to  the  heart  heat.  The  nuiscular  walls  of  the  different  chambers 
of  the  heart  vary  in  thickness,  according  to  the  amount  of  work  per- 
formed by  these  parts.  The  walls  of  the  auricles  are  thin  as  the  press- 
ure in  these  chambers  is  always  comparatively  low;  the  walls  of  the 
left  ventricle,  on  the  other  hand,  are  very  thick,  as  it  must  propel  the 
blood  against  the  high  pressure  in  the  systemic  vessels.  The  right 
ventricular  walls  are  thinner  than  the  left,  as  the  pressure  in  the  lung 
vessels,  into  which  the  right  ventricle  pumps  its  contents,  is  much 
lower  than  the  pressure  in  the  systemic  vessels.  The  internal  surface 
of  the  the  heart  is  lined  with  a  single  layer  of  cells,  this  layer  is  con- 
tinuous throughout  the  whole  circulatory  system  and  reduces  fric- 
tion by  offering  a  smooth  surface  to  the  rapidly  flowing  blood.  The 
movements  of  the  heart  consist  of  the  alternate  contraction  and  relaxa- 
tion of  the  heart  walls.  Each  heart  heat  is  divided  into  three  stages: 
(1)  The  contraction  of  the  auricles;  this  is  rapidly  followed  by  (2)  the 
contraction  of  the  ventricles  during  which  the  auricles  relax;  and  (3) 
a  pause  during  which  both  auricles  and  ventricles  "are  relaxed. 

The  heart  is  so  designed  that  two  streams  of  blood  are  pumped 
simultaneously.  The  right  side  of  the  heart  receives  the  blood  on  its 
return  from  the  tissues  and  pumps  it  into  the  lung  vessels  where  a 
fresh  supply  of  oxygen  is  absorbed  and  carbon  dioxide  given  off. 
The  left  side  of  the  heart  receives  the  blood  after  its  transit  through 
the  lungs  and  discharges  the  now  aerated  blood  into  the  systemic 
vessels  to  be  distributed  throughout  the  body. 

The  Bloodvessels. — The  tubes  or  vessels  through  which  the  blood 
circulates  are  divided  according  to  their  structure  and  function  into 
arteries,  arterioles,  capillaries,  venules,  and  veins. 

The  arteri&s,  vessels  which  conduct  the  blood  away  from  the  heart, 
are  made  up  of  three  layers,  an  internal  layer  of  flat  cells,  a  middle 
muscular  layer  containing  numerous  elastic  fibers  and  an  outer  layer 
of  tough  connective  tissue.  To  this  structure  the  arteries  owe  their 
great  elasticity  and  strength.  Strength  is  essential  to  resist  the  great 
pressure  in  these  vessels,  and  the  elasticity  permits  the  arteries  to 
distend  at  each  heart  beat  and  thus  to  accommodate  the  three  or 
four  ounces  of  blood  suddenly  expelled  into  their  lumen  by  the  con- 
traction of  the  ventricles.  The  arteries  branch  repeatedly,  each  suc- 
cessive division  giving  rise  to  smaller  and  smaller  vessels  until  the 
arterioles  are  reached.  The  latter  differ  from  the  arteries  in  that  their 
external  and  middle  layers  are  much  thinner  and  contain  very  little 
elastic  tissue.  These  vessels,  being  under  control  of  the  nervous  system, 
are  able  to  contract  or  dilate  under  stimulation.  By  this  mechanism 
the  amount  of  blood  circulating  through  any  organ  is  regulated. 

The  arterioles  subdivide  like  the  arteries  and  terminate  in  minute 
vessels  known  as  capillaries.     The  capillaries,  consisting  only  of  a 


120  PHYSIOLOGY 

single  layer  of  flat  cells,  form  a  network  of  microscopic  tubes  the  meshes 
of  which  are  occupied  by  the  cells.  Owing  to  the  thinness  of  the  capil- 
lary walls,  plasvia  diffuses  readily  into  the  spaces  of  this  capillary  net- 
work and  in  this  way  the  albumin,  sugar,  and  other  foods  contained 
in  the  plasma  are  brought  into  immediate  contact  with  each  cell  of 
the  body.  Oxygen  diffuses  likewise  from  the  red  blood  cells  into  the 
intercapillary  spaces  where  it  is  absorbed  by  cells.  The  carbon  dioxide 
and  oilier  excretory  products  of  the  cells  passing  in  the  opposite  direc- 
tion, enter  the  blood  through  the  capillary  walls  and  are  carried  away 
by  the  circulation  to  be  excreted  from  the  body. 

The  network  of  capillaries  formed  by  the  division  of  each  arteriole 
unite  again  to  form  vessels  known  as  venules;  the  later  in  turn  join 
to  form  larger  vessels,  called  veins,  w^hich  return  the  blood  to  the  heart. 
The  veins,  like  the  arteries,  are  composed  of  three  coats.  In  the 
veins,  however,  the  outer  coats  are  much  thinner,  as  the  pressure  in 
the  veins  is  considerably'  lower  than  that  in  the  arteries.  The  veins 
are  furnished  with  valves  which  permit  the  passage  of  blood  only  in 
the  direction  of  the  heart. 

As  has  been  seen,  the  heart  is  composed  of  two  distinct  halves — the 
right  side  of  the  heart  pumping  blood  into  the  lungs,  the  left  side 
forcing  blood  throughout  the  body.  There  are  therefore  two  systems 
of  bloodvessels,  one  between  the  right  ventricle  and  left  auricle,  the 
other  between  the  left  ventricle  and  the  right  auricle.  The  first  is 
known  as  the  pnJinonary  circulation,  the  second  as  the  systemic  cir- 
culation. 

The  Pulmonary  Circulation. — The  blood  returning  to  the  heart  after 
its  circulation  through -the  tissues,  enters  the  right  auricle  through  two 
large  \'eins,  the  inferior  and  superior  vena  cava.  It  then  passes  into 
the  relaxed  right  ventricle.  The  right  auricle  contracts  and  thus  com- 
pletes the  filling  of  the  ventricle.  The  auricles  now  relax  and  the 
ventricles  contract.  As  the  pressure  in  this  chamber  increases,  the 
blood  i)rcssing  against  the  under  surface  of  the  tricuspid  vcdve  (between 
right  auricle  and  \'entricle)  brings  about  its  closure. 

When  the  pressure  in  the  right  ventricle  exceeds  that  in  the  pul- 
monary artery,  the  semihinar  valve,  situated  at  the  outlet  of  the  ven- 
tricle, opens  so  that  the  blood  is  forced  into  this  vessel.  After  ven- 
tricular contraction  has  reached  its  height  relaxation  commences,  and 
the  pressure  in  the  pulmonary  artery  closes  the  semilunar  valve. 
The  pulmonary  artery  di\'ides  into  branches  which  enter  the  substance 
of  the  lungs.  Within  the  hings,  these  branches  sul)divide  into  arte- 
rioles and  the  latter  into  ca])illaries  which  form  a  network  about  the 
respiratory  chambers  (alveoli). 

The  blood  during  its  passage  through  the  lung  capillaries  throws 
off  carbon  dioxide  and  absorbs  a  fresh  suj)])ly  of  oxygen.  The  lung 
capillaries  empty  into  venules,  the  veiniles  unite  to  form  veins  which 
finally  emj^ty  the  oxygenated  blood  into  the  left  auricle  by  way  of 
four  large  vessels,  the  pnhnonary  veins. 


PHYSIOLOGY  OF   THE  CIRCULATION  121 

The  Systemic  Circulation. — The  blood  returning  from  tlie  lungs 
passes  from  the  left  auricle  into  the  left  ventricle,  the  filling  of  this 
chamber  is  aided  by  the  contraction  of  the  auricle.  The  left  ventricle 
then  contracts,  and  the  auricle  relaxes.  The  rising  pressure  in  the 
ventricle  closes  the  mitral  valve  (between  the  left  auricle  and  ventricle), 
and  opens  the  aortic  semilunar  valve,  so  that  the  contents  of  the  ven- 
tricle are  forced  into  the  aorta,  a  large  artery  which  through  its  branches 
carries  the  aerated  blood  to  all  parts  of  the  body.  As  the  ventricle 
relaxes  the  pressure  in  the  aorta  closes  the  aortic  valve.  The  blood 
passes  successively  through  arteries,  arterioles  and  capillaries.  In  the 
capillaries  the  oxygen  and  food  is  distributed  to  the  cells  and  carbon 
dioxide  and  other  excretory  products  removed.  The  blood  then 
passes  from  the  capillaries  into  venules,  next  into  veins,  and  finally 
returns  to  the  right  auricle  by  way  of  the  two  large  veins,  the  iuferior 
and  superior  vena  cava. 

The  Portal  Circulation. — Associated  with  the  organs  of  alimentation 
and  of  special  importance  during  digestion  is  a  third  system  of  vessels 
known  as  the  portal  circulation.  The  veins  of  the  abdominal  alimen- 
tary organs  do  not  pass  directly  into  the  vena  cava  but  unite  to 
form  a  large  vessel,  the  portal  vein,  which  enters  the  liver.  In  the  liver 
the  portal  vein  subdivides  into  capillaries  which  form  a  close  network 
about  the  liver  cells.  From  this  capillary  network  arise  veins,  which 
unite  to  form  the  hepatic  vein,  which  in  turn  empties  into  the  inferior 
vena  cava.  The  alimentary  organs  receive  their  blood  supply  from 
branches  of  the  aorta.  In  the  mucous  membrane  of  the  stomach  and 
intestines  these  branches  subdivide  in  capillaries.  Here  the  capillaries 
serve  a  twofold  purpose,  they  carry  aerated  blood  to  the  cells  of  these 
organs,  and  during  digestion  convey  the  absorbed  peptones  and  sugars 
to  the  liver  by  way  of  the  portal  vein.  In  the  liver  the  capillaries 
arising  from  the  portal  vein  bring  these  peptones  and  sugars  in  close 
contact  with  the  liver  cells.  The  excess  of  sucjar  is  converted  into 
glycogen  which  is  stored  in  the  liver  for  future  use  and  the  peptones 
are  modified  and  carried  away  in  the  blood  plasma  to  be  distributed 
to  all  cells  of  the  body. 

The  Lymphatic  System. — ^Related  to  the  circulation  of  the  blood  is 
another  system  of  vessels  known  as  lymphatics.  The  lymphatics  begin 
as  exceedingly  minute  vessels  which  arise  from  the  spaces  between 
the  cells.  These  intercellular  spaces  contain  fluid  derived  from  the 
plasma  of  the  blood  which  has  diffused  through  the  capillary  walls. 
The  small  lymphatics,  therefore,  drain  off  this  fluid  after  the  food 
originally  contained  in  it  has  been  absorbed  by  the  cells.  The  excre- 
tory products  are  not  entirely  removed  by  the  blood  so  that  the  fluid 
carried  away  by  the  lymphatics  contains  part  of  the  excretions  of  the 
cells.  The  lymphatics  unite  to  form  large  vessels  which  empty  at 
intervals  into  the  lymphatic  glands.  In  these  glands  wdiite  blood  cor- 
puscles are  formed  and  are  eventually  carried  into  the  blood  stream 
by  the  lymphatic  channels.     From  the  lymphatic  glands  the  lymph 


122  PHYSIOLOGY 

passes  into  larger  vessels  which  unite  to  form  the  right  and  Jeff  thoracic 
ducts. 

The  right  thoracic  duct  is  a  short  vessel  which  drains  the  lymph  from 
the  right  side  of  the  head,  the  right  arm  and  the  corresponding  half 
of  the  thorax.     It  empties  into  veins  situated  at  the  root  of  the  neck. 

The  left  thoracic  duct  is  a  long  vessel  which  drains  the  remaining 
lymphatics  of  the  body  including  those  of  the  intestines.  The  lymph 
capillaries  in  the  villi  of  the  small  intestines  are  concerned  principally 
with  the  absorption  of  fats  during  digestion.  The  absorbed  fats  are 
thus  thrown  directly  into  the  blood  stream  by  way  of  the  left  thoracic 
duct  which  also  empties  in  veins  at  the  root  of  the  neck. 

The  lymphatic  vessels,  like  the  veins,  are  supplied  with  valves 
which  allow  the  Ij^mph  to  flow  only  in  the  direction  described. 

PHYSIOLOGY    OF   EXCRETION. 

The  maintenance  of  health  in  any  organism  depends  upon  the 
constant  removal  of  the  excretory  products  arising  from  the  metabolism 
of  its  cells. 

The  most  important  excretory  products  are  carbon  dioxide,  urea, 
uric  acid,  sulphates,  phosphates,  chlorides,  and  water. 

Carbon  dioxide,  as  we  have  seen,  results  principally  from  oxidative 
processes  in  the  cells. 

Urea  and  uric  acid  are  the  final  products  in  the  breaking  down  of 
protoplasmic  material  and  represent  not  only  cellular  wastes,  but  also 
the  decomposition  of  protein  foodstuffs  after  their  absorption  from  the 
alimentary  tract. 

The  sulphates,  p)hosphates,  chlorides,  and  water  are  derived  partly 
from  cellular  changes,  and  partly  from  the  amount  of  these  substances 
absorbed  during  digestion  in  excess  of  the  needs  of  the  cells. 

These  products,  constantly  excreted  into  the  blood  and  lymph,  are 
conveyed  by  the  circulation  to  the  excretory  organs  where  means  are 
pro\'ided  for  their  removal. 

Excretory  Organs. — The  organs  concerned  in  the  removal  of  these 
products  are  the  lungs,  the  skin,  and  the  kidneys,  accordingly  the.y  are 
known  as  the  organs  of  excretion. 

The  lungs,  the  function  of  which  has  already  l)een  considered, 
excrete  practically  all  the  carbon  dioxide  formed  in  the  body  and  in 
addition  about  a  pint  of  water  daily. 

"The  sJci7i,  besides  its  excretory  function,  plays  other  important 
parts  in  the  economy  of  the  body. 

The  skin  is  di\ided  into  an  external  layer,  the  epidermis,  or  scarf 
skin,  and  an  internal  layer,  the  dermis,  or  true  skin.  The  epidermis 
consi.sts  of  numerous  superimposed  cells,  the  uppermost  of  which  are 
dead,  and  constantly  dro])j)ing  off.  The  cells  thus  lost  are  replaced 
by  the  inulti])Hcation  of  cells  at  the  bottom  of  this  layer.  The  epi- 
dermis  has   no   bloodvessels   and   dcrixcs   its   nourishment  from   the 


PHYSIOLOGY  OF  EXCRETION  123 

lymph  which  escapes  thn)uji;h  the  walls  of  capillaries  in  the  true  skin, 
and  this  accounts  for  the  death  of  the  externally  situated  cells  which  are 
unable  to  obtain  a  sufficient  supply  of  food.  The  junction  of  the 
epidermis  is  a  protective  one.  It  covers  the  entire  surface  of  the  body, 
and  by  its  horny  texture  prevents  injury  to  the  underlying  tissues. 

The  internal  layer  of  the  skin  or  dermis,  upon  which  the  epidermis 
lies,  is  made  up  of  numerous  interlaced  connective-tissue  fibers  richly 
supplied  with  bloodvessels  and  nerves.  The  dermis  at  its  point  of 
contact  with  the  epidermis  is  studded  with  papillae,  minute  finger-like 
elevations,  which  contain  loeps  of  capillary  vessels.  Many  of  the 
papilke  contain  in  addition  sensory  end-organs  through  which  external 
impressions  are  received.  The  function  of  the  skin  as  a  sensory  organ 
will  be  again  mentioned  under  the  nervous  system. 

Two  important  sets  of  structures  situated  in  the  dermis  are  the 
sebaceous  and  sweat  glands. 

The  sebaceous  glands  consist  of  minute  sacs  lined  with  a  single  layer 
of  cells,  each  sac  emptying  into  a  common  channel  which  opens  into 
a  hair  follicle.  The  cells  of  these  glands  have  the  property  of  manu- 
facturing, from  substances  derived  from  the  blood,  an  oily  secretion 
which  passes  to  the  skin  surface  through  the  hair  follicles.  The 
purpose  of  this  secretion  is  to  keep  the  skin  soft  and  pliant  and  prevent 
the  drying  of  the  hair. 

The  sweat  glands  are  composed  of  a  single  tube  also  lined  with  a 
single  layer  of  cells.  This  tube  is  coiled  several  times  upon  itself  and 
opens  externally  by  a  straight  duct  which  passes  through  the  epidermis. 
The  openings  of  these  ducts  are  called  pores.  The  coiled  portion  of 
the  gland  is  surrounded  by  a  network  of  capillaries,  so  that  the  blood 
is  brought  in  close  contact  with  the  gland  cells.  The  latter  by  their 
selective  action  remove  certain  materials  from  the  blood  which  are 
then  excreted  through  the  pores.  This  excretion,  know^n  as  sweat, 
consists  of  water,  carrying  in  solution  salts  and  a  small  amount  of  urea, 
carbon  dioxide,  and  fatty  acids.  To  the  latter  the  peculiar  odor  of 
this  excretion  is  due. 

The  arterioles  of  the  dermis,  in  conjunction  with  the  excretion  of 
sweat,  play  an  important  part  in  the  heat  regulation  of  the  body. 
During  exercise  when  an  enormous  amount  of  heat  is  generated  by 
the  activity  of  the  muscle  cells,  the  bloodvessels  of  the  skin  dilate  and 
the  secretion  of  sweat  increases.  The  dilatation  of  the  skin  vessels 
brings  the  overheated  blood  to  the  surface  in  great  quantities,  where 
it  loses  heat  by  radiation,  the  external  air  being  cooler  than  the 
blood.  The  sweat,  on  the  other  hand,  evaporates  rapidly  and  in  this 
way  causes  a  marked  loss  of  heat. 

If  the  skin  is  exposed  to  cold  the  reverse  occurs,  the  bloodvessels  of 
the  skin  become  constricted  and  the  secretion  of  sweat  diminishes.  In 
this  way  heat  loss  is  prevented. 

The  kidneys  are,  with  the  lungs,  the  most  important  organs  of  excre- 
tion.   The  lungs  are  concerned  principally  with  the  excretion  of  carbon 


124  PHYSIOLOGY 

dioxide  and  the  kidneys  with  the  greater  part  of  the  soHd  excretory 
products  as  only  a  small  portion  of  these  products  are  excreted  through 
the  skin. 

The  urine,  the  fluid  resulting  from  the  activity  of  the  kidneys,  con- 
sists of  an  aqueous  solution  of  urea,  uric  acid,  phosphates,  sulphates, 
chlorides,  a  very  small  quantity  of  carbon  dioxide  and  pigment.  To 
the  latter  the  characteristic  color  of  the  urine  is  due. 

The  kidneys,  two  in  number,  are  situated  in  the  upper  part  of  the 
abdominal  cavity  on  either  side  of  the  spinal  column.  These  organs 
are  bean-shaped  with  their  concavity  facing  the  spine. 

From  the  stand-point  of  function  the  essential  parts  of  the  Jcidney  are : 
(1)  The  tubules,  the  cells  of  which  by  their  selective  action  remove  solid 
excretory  products  and  water  from  the  blood.  (2)  The  bloodvessels 
which  convey  the  blood  to  the  tubules.  (3)  The  pelvis  of  the  kidney 
into  which  the  tubules  empty  their  contents. 

The  tubules  of  the  kidneys  with  their  related  bloodvessels  form  little 
systems,  which  are  exceedingly  numerous,  but  as  these  systems  are 
all  alike  in  structure  and  function,  the  description  of  a  single  one 
will  suffice. 

The  tubules,  little  tubes  consisting  of  a  single  layer  of  cells,  begin  as 
minute  blind  pouches  near  the  external  surface  of  the  kidney.  These 
pouches  may  be  compared  to  the  inverted  tip  of  the  finger  of  a  glove. 
The  blind  extremity  of  the  tubules  is  thus  composed  of  two  layers 
of  flat  cells,  an  internal  layer  forming  a  dilated  cavity  and  an  external 
layer  continuous  below  with  the  walls  of  the  tubules.  Into  this  dilated 
cavity  an  arteriole  enters  which  immediately  divides  into  a  network 
of  capillaries.  This  portion  of  the  tubule  with  its  capillary  tuft  is  called 
a  Malpighian  corpuscle.  Soon  after  leaving  its  blind,  pouched  extrem- 
itj^  the  tubule,  from  now  on  lined  with  a  single  layer  of  cubical  cells, 
is  coiled  spirally  for  a  few  turns  (proximal  convolution)  and  then  dips 
down  in  a  straight  line  for  a  short  distance  toward  the  concavity  of 
the  kidney;  it  then  bends  back  upon  itself  and  returns  to  a  position 
near  its  point  of  origin,  where  it  forms  a  second  series  of  coils  (the 
distal  convolution).  Both  the  first  and  second  coils  of  the  tubule  are 
surrounded  by  netAvorks  of  capillaries. 

The  tubule  after  leaving  the  distal  convolution  enters  collecting 
tubules,  which,  joining  with  tubules  of  other  similar  systems,  run  in  a 
straight  course  toward  the  concavity  of  the  kidney  and  empty  by 
small  openings  into  the  i)elvis  of  this  organ. 

The  secretion  of  vrinc  takes  ])lace  in  the  following  maimer.  The 
blood  which  contains  the  excretory  prcxlucts  reaches  the  kidney  by  way 
of  the  renal  artery,  a  branch  of  the  aorta.  The  renal  artery  subdivides 
into  brunches,  which  on  entering  the  concave  side  of  the  kidney, 
divide  into  mmierous  arterioles.  These  arterioles  pass  between  the 
collecting  tubules  and  near  the  external  surface  of  the  kidney  give 
off  branches  which  enter  the  blind  pouches  formed  by  the  infolding 
of  the  extremities  of  the  tubules  (the  Malpighian  corpuscle).     Each 


PHYSIOLOGY  OF   THE  NERVOUS  SYSTEM  125 

pouch  receives  an  arteriole  which  (Hvides  into  a  tuft  of  capiUaries.  At 
this  point  a  process  of  selective  filtration  takes  {)lace.  The  icater  and 
salts  to  be  excreted  from  the  blood  filter  through  the  capillary  walls 
and  then  through  the  single  layer  of  cells  forming  the  wall  of  the 
tubule  and  thus  collect  in  the  interior  of  the  latter. 

From  the  capillary  tuft  just  described  a  small  vein  arises  which 
carries  the  blood  along  to  the  proximal  and  distal  convolutions  of  the 
urinary  tubules.  There  the  vein  again  divides  into  a  second  network 
of  capillaries.  The  cells  of  the  tubules  at  this  point  have  the  power 
of  sch'cfiiif/  certain  substances  from  the  blood,  such  as  urea  and  uric 
acid,  and  at  the  same  time  of  reabsorbing  the  excess  of  the  waiter  which 
has  passed  into  the  tubule  from  the  first  system  of  capillaries. 

The  blood,  now  relieved  of  excretory  products,  is  collected  by  veins 
which,  joining  with  other  similar  vessels,  empty  into  the  renal  vein,  a 
tributary  of  the  inferior  vena  cava. 

The  urine  after  its  passage  through  the  course  of  the  tubules  enters 
the  pelvis  of  the  kidney.  F'rom  this  dilated  sac  the  m-ine  passes 
through  the  ureter  into  the  bladder,  where  it  collects  until  voided  by 
the  act  of  micturition. 

PHYSIOLOGY    OF    THE    NERVOUS    SYSTEM. 

The  function  of  the  nervous  system  is  purely  correlative.  Through 
the  activity  of  its  units,  the  nerve  cells,  it  brings  organs  into  intimate 
relation  and  thus  harmonizes  their  vital  processes,  and  through  recep- 
tive organs,  those  of  the  special  senses,  it  relates  the  body  as  a  whole 
to  its  external  surroundings. 

The  Nerve  Cell. — The  functional  unit  of  the  nervous  system  is  the 
nerve  cell  or  neuron.  The  neuron  consists  of  a  nucleated  cell  body 
from  which  issue  two  or  more  protoplasmic  processes,  the  nerve  fibers. 

When  a  nerve  cell  is  stimulated  either  by  chemical  or  physical 
causes,  a  current  arises  which  is  known  as  a  nervous  iuipnlse.  This 
impulse,  which  may  be  aroused  from  changes  at  the  periphery  of  the 
fiber  or  in  the  nerve  cell  body,  is  transmitted  by  the  nerve  fiber  in  a 
way  comparable  to  a  current  of  electricity  travelling  through  a  ware. 

Nerve  Fibers. — The  nervous  impulse  in  its  course  through  the  nerve 
fiber,  always  travels  in  a  definite  direction,  accordingly  all  neurons  are 
divided  into  three  large  classes:  (1)  The  afferent  neurons ,  the  fihevs 
of  which  convey  impulses  from  all  parts  of  the  body  to  central  stations 
in  the  nervous  system.  (2)  The  efferent  neurons  which  conduct  impulses 
from,  these  central  stations  to  the  cells  of  all  the  organs.  (3)  The 
neurons  which  transmit  impulses  from  one  nerve  cell  to  the  other. 

Receptive  Organs. — The  afferent  nerves  are  supplied  at  their  point  of 
origin  with  specialized  structures  known  as  receptive  organs.  These 
receptors  are  part  of  the  nei-ve  fiber  and  are  adapted  to  receive  impres- 
sions arising  from  changes  in  the  surroundings  of  the  organisms  or 
from  changes  in  its  tissues.     These  receptive  organs  and  the  afferent 


126  PHYSIOLOGY 

ne^^■es  to  which  they  are  attached  are  speciaHzed  in  function  and  so 
respond  best  to  one  particuhir  form  of  stimnhition. 

To  illustrate:  Tlie  receptive  organs  of  the  skin  receive  impressions 
of  pain,  heat,  cold,  touch,  and  pressure.  When  an  object  is  brought 
in  contact  with  the  skin,  the  receptive  organs  of  touch  are  stimulated. 
They  originate  an  impulse  which  is  conducted  through  the  fiber  to 
the  central  nervous  system  where  our  consciousness  translates  this 
impulse  into  the  sensation  of  touch. 

If  the  skin  is  pricked  with  a  pin,  receptive  organs  of  pain  are  stimu- 
lated and  a  sensation  of  pain  is  aroused.  In  this  w^ay  the  organism  is 
acquainted  with  immediate  external  changes  and  can  respond  accord- 
ingly. 

Situated  in  the  joints,  tendons,  and  muscles  are  receptive  organs 
which  give  us  what  is  known  as  the  muscle  sense.  This  sense  enables 
us  even  with  our  eyes  closed,  to  determine  the  exact  position  assumed 
by  our  limbs,  trunk,  and  head. 

The  receptive  organs  of  sight  are  located  in  the  retina  of  the  eye. 
Light  waves  entering  through  the  pupil  stimulate-  afferent  nerves, 
the  impulse  is  conveyed  to  the  brain  and  gives  rise  to  the  perception 
of  color  and  shape. 

In  the  upper  part  of  the  nasal  cavity,  lying  in  the  mucous  membrane 
are  the  receptive  organs  of  smell.  Volatile  substances  coming  in 
contact  with  these  endings,  give  rise  to  olfactory  sensations. 

The  internal  ear  contains  two  sets  of  receptive  organs,  one  sensitive 
to  air  vibrations  and  through  which  w^e  perceive  sound,  the  other  trans- 
mitting the  impulses  which  regulate  the  equilibrium  of  the  body. 

The  sense  of  taste  arises  from  the  stimulation  of  endings  in  the 
mucous  membranes  at  the  posterior  part  of  the  tongue. 

All  the  internal  organs  are  also  supplied  with  afferent  fibers  which 
conduct  impulses  centrally. 

The  efferent  nerve  fibers  which  con\'ey  impulses  peripherally'  to  the 
cells  of  the  body  are  divided  into  three  classes:  (1)  The  motor  nerves. 
(2)  The  secretory  nerves.     (3)  The  inhibitory  nerves. 

The  motor  nerves  carry  impulses  to  the  muscle  cells  and  thus  bring 
about  their  contraction.  The  voluntary  muscles  are  supplied  by 
motor  neurons  arising  from  the  central  nervous  system.  The  smooth 
muscles  of  the  bloodvessels  and  the  internal  organs  are  supplied  by 
motor  fibers  from  the  sympathetic  system. 

The  secretory  nerves  are  deriy'cd  from  the  sympathetic  system  and 
terminate  in  gland  cells  throughout  the  body.  It  is  the  stimulation 
of  such  nerves  that  activates  the  fiow  of  secretions,  i.  e.,  the  saliva, 
the  gastric  juice,  etc. 

The  inhibitory  nerves,  also  branches  of  the  sympathetic  system, 
supply  the  muscle  cells  of  the  heart  and  bloodvessels.  Their  function 
is  to  suppress  or  diminish  the  activity  of  these  structures.  P^.xamples 
of  these  are  the  vagus  nerve,  wliich  slows  tiic  heart  rate,  and  the  vaso- 
dilator nerves,  which  bring  about  the  relaxation  of  bloodvessels. 


PHYSIOLOGY  OF   THE  NERVOUS  SYSTEM  127 

In  the  central  and  symi)athetic  nervous  system  the  afferent  and 
efferent  nerves  are  brought  into  relation  with  each  other  in  such  a 
way  that  any  afferent  ini])ulse  arising  from  the  periphery  is  always 
followed   by   a    suitable   cflVrent   response. 

The  Central  Nervous  System. — The  central  nervous  system  includes 
from  below  upward,  the  spinal  cord,  the  medulla,  the  cerebellum,  and 
the  cerebrum. 

The  spinal  cord  presents  on  cross-section  a  butterfly-shaped  area, 
grayish  in  color,  and  made  up  of  numerous  nerve-cell  Ixxlies  anfl  their 
fibers.  Situated  anteriorly  in  this  gray  matter  are  the  cell  bodies  of 
the  spinal  motor  neurons,  the  fibers  of  which  supply  the  voluntary 
muscles.  The  gray  matter  is  surrounded  by  bundles  of  nerve  fibers 
(white  matter)  which  run  u])  and  down  the  cord,  their  cell  bodies 
lying  at  higher  or  lower  levels. 

From  the  anterior  portion  of  the  cord  at  the  level  of  each  \ertebra 
two  large  nerve  trunks  arise,  one  on  either  side.  These  trunks  are 
known  as  the  anterior  roots  and  contain  the  fibers  of  the  spinal  motor 
neurons. 

From  the  posterior  aspect  of  the  cord  and  at  corresponding  levels 
arise  similarly  the  posterior  roots.  These  two  trunks  consist  of  afferent 
or  sensory  fibers  which  conduct  impulses  from  the  periphery  to  the 
spinal  cord. 

A  short  distance  away  from  the  spinal  cord  the  anterior  and  pos- 
terior roots  on  each  side  join  to  form  a  single  bundle,  known  as  a 
spinal  nerve.  Just  before  "joining  with  the  anterior  root,  the  posterior 
root  presents  an  enlargement,  the  spinal  ganglion,  which  contains  the 
cell  bodies  of  the  afferent  or  sensory  nerve  fibers. 

The  spinal  nerves,  of  which  there  are  thirty-one  pairs,  pass  out  per- 
ipherally and  by  their  subdivisions  bring  afferent  and  efferent  fibers  in 
contact  with  the  tissues  supplied  by  each  spinal  nerve. 

Reflex  Nervous  Action.— The  most  primitive  fimction  of  the  nervous 
system  is  a  simple  refle.x  action.  The  simple  reflex  involves  only  two 
neurons,  an  afferent  and  an  efferent.  The  path  taken  by  the  impulse 
is  as  follows:  From  the  stimulation  of  a  receptive  organ  an  impulse 
arises  which  passes  through  the  afferent  neuron  and  enters  the  spinal 
cord  through  the  posterior  root.  In  the  cord  the  afferent  fiber  sub- 
divides into  fibrils  (terminal  arborizations)  which  are  in  contact  with 
motor  neurons.  The  impulse  passing  through  this  point  of  contact  is, 
so  to  speak,  transferred  to  the  motor  neurons  which  pass  out  of  the 
cord  through  the  anterior  roots  and  convey  the  impulse  to  the  muscles 
they  supplv.  The  result  is  a  muscular  response  not  controlled  by  the 
will. 

Reflex  action  always  involves  an  afferent  path,  which  may  be  repre- 
sented by  any  afferent  nerve,  and  efferent  paths  through  motor,  secre- 
tory or  inhibitory  nerves. 

Not  only  in  the  spinal  cord,  but  throughout  the  entire  nervous  sys- 
tem, we  find  reflex  paths,  some  more  complicated  than  others,  through 


128  PHYSIOLOGY 

which  important  functions  of  the  body  are  regulated.  As  an  example 
of  these  ^egulati^'e  reflexes  may  be  mentioned  the  profuse  reflex  flow  of 
saliva  and  gastric  juice  which  follows  the  stimulations  of  the  nerves 
of  taste. 

The  white  matier  of  the  spinal  cord  contains  bundles  of  fibers 
which  act  as  connecting  paths  between  the  peripheral  afferent  and 
efferent  neurons  and  the  higher  iterve  centers  of  the  cerebrum  and  the 
cerebellum. 

The  Higher  Motor  Paths. — Among  these  higher  nerve  centers  are  the 
voluntary  }itotur  neurons  which  are  situated  in  the  cortex  or  gray  matter 
of  the  cerebrum,  on  its  lateral  aspect.  In  this  area  arise  motor 
impulses  originated  by  the  will.  The  fibers  of  these  neurons  pass  into 
the  medulla  (the  first  part  of  the  cord)  where  the  greater  part  of  them 
cross  over  to  the  opposite  side  from  which  they  originated,  and  then, 
passing  on  through  the  medulla,  run  down  the  spinal  cord.  At  dif- 
ferent levels  individual  fibers  leave  this  motor  bundle  or  tract  as  it 
is  called  and  by  their  terminations  come  in  contact  with  the  spinal 
motor  neurons  of  corresponding  levels. 

Owing  to  the  crossing  of  the  fibers  in  the  medulla,  each  half  of  the 
brain  controls  voluntary  motion  on  the  opposite  side  of  the  body. 
Therefore  when  a  part  of  the  body  is  voluntarily  moved  as,  for  example, 
the  left  index  finger,  the  impulse  arises  in  the  brain  cortex  on  the  right 
side  and  travels  to  the  medulla  where  it  crosses  to  the  left  side;  it 
then  continues  its  course  down  the  spinal  cord  and  at  the  level  of  the 
arms  passes  over  to  the  spinal  motor  neurons  which  then  convey  the 
impulse  to  the  muscles  concerned  in  moving  the  part. 

The  Higher  Sensory  Paths. ^ — Thus  far  only  the  peripheral  afferent 
neuron  has  been  considered  and  the  part  it  plays  in  reflex  activity. 
But  as  the  ability  to  perceive  sensations  resides  in  the  brain,  path- 
ways are  required  to  transmit  impulses  from  these  afferent  nerves  to 
this  organ. 

The  sensory  nerve  fibers  after  their  entrance  into  the  cord,  divide 
into  tico  parts:  one,  as  already  mentioned,  comes  in  contact  with 
adjoining  motor  neurons;  the  other  ascends  the  posterior  portion  of 
the  spinal  cord  and  ends  in  the  medulla.  At  this  point  are  located 
other  cell  bodies  which  through  their  fibers  complete  the  path  to  the 
brain.  These  fibers,  like  the  motor  fibers,  cross  to  the  opposite  side 
and  end  in  the  cortex  just  behind  the  cell  bodies  of  the  voluntary 
motor  neurons. 

The  Cerebellum. — The  spinal  cord  contains  other  nerve  paths  which 
relate  afferent  anfl  efferent  nerves  with  the  cerebellum,  and  this  organ 
is  in  turn  related  to  the  cerebrum  by  nerve  paths.  The  function  of 
the  rcrebrllum  is  to  coordinate  muscular  movement. 

The  Medulla. — The  medulla  is  the  continuation  of  the  upper  part 
of  the  spinal  cord  and  gives  origin  to  some  of  the  cranial  nerves. 
Through  it  course  the  afferent  and  efferent  nerve  i)aths  which  bring 
into  relation  the  spinal  cord  with  the  cerebrum  and  cerebellum.  The 
medulla  is  of  great  importance,  for  it  is  the  seat  of  nerve  centers  which 


PHYSIOLOGY  OF  THE  NERVOUS  SYSTEM  129 

control  the   vital  fuitction.s.     In   it   are    located    the  respiratory,   the 
cardiac  and  the  vasomotor  centers. 

The  rcspiratori/  coder  contains  cell  bodies  the  fil)ers  of  which  run 
down  the  spinal  cord  where  they  connnunicate  with  the  motor  neurons 
supplying  the  muscles  involved  in  the  respiratory  act.  The  function 
of  this  center  has  been  considered  under  Respiration. 

The  cardiac  centers  regulate  the  heart  rate  through  two  important 
nerves,  the  vagti.s'  and  the  acceleratur.  The  vagus  decreases  the  heart 
rate  and  the  accelerator  increases  it. 

The  vasomotor  center  contains  cell  bodies  which  carry  impulses  to 
the  muscle  of  the  bloodvessel  walls  through  the  vasoconstrictor  and 
vasodilator  nerves.  The  former  constrict  the  bloodvessels,  thus 
raising  the  blood-pressure,  while  the  latter  have  exactly  the  opposite 
effect  and  lower  blood-pressure. 

The  Cerebrum. — The  cerebrum  is  composed  of  gray  and  white  matter. 
The  gray  matter,  made  up  of  numerous  cell  bodies  and  their  fibers,  is 
distributed  into  two  groups,  the  cortex  and  the  l)asal  ganglia. 

The  cortex,  the  surface  of  which  is  greatly  increased  by  numerous 
folds  or  convolutions,  is  divided  into  three  functional  areas:  the 
motor,  the  sensory  and  the  higher  psychic. 

The  motor  areas  control  voluntary  motor  activity. 

The  sensory  areas  are  locatefl  in  various  regions  of  the  cortex,  each 
area  recei\'ing  the  final  nervous  paths  of  one  particular  special-sense 
organ. 

All  these  regions  of  the  cortex  are  in  turn  intimately  related  by 
nervous  connections  with  the  psychic  areas  from  which  the  higher 
mental  processes  originate. 

The  basal  ganglia  are  series  of  nerve  cell  masses,  at  the  base  of  the 
brain. 

The  white  matter  consists  of  the  motor  and  sensory  paths  already 
mentioned  and  nerve  fibers  connecting  the  different  areas  of  the 
brain. 

The  Sympathetic  Nervous  System, — ^This  system  consists  of  ganglia 
and  numerous  communicating  and  distributing  nerve  fibers. 

The  ganglia  form  two  principal  groups,  (a)  those  of  the  ganglionated 
cord  on  either  side  of  the  spinal  column,  and  (6)  the  more  peripherally 
situated  ganglia  of  the  plexuses  of  the  thoracic,  abdominal,  and 
pelvic  cavities.  Collections  of  sympathetic  neurons  are  also  found  in 
the  wall  of  the  visceral  organs,  /.  e.,  the  heart,  intestines,  etc. 

The  important  efferent  branches  of  the  sympathetic  system  are  the 
following.  The  pupil-dilating  fibers  which  bring  about  the  dilatation 
of  the  pupil;  the  vasomotor  nerves  (vasoconstrictors  and  dilators)  con- 
trolled by  the  vasomotor  center  in  the  medulla;  the  motor  fibers  to 
the  smooth  muscle  cells  of  the  alimentary  tract;  the  secretory  nerves 
supplying  all  the  gland  cells  of  the  body;  and  the  nerves  regulating  the 
rate  of  the  heart. 

The  afferent  sympathetic  nerves  convey  impulses  from  the  visceral 
organs  to  reflex  centers  in  the  central  nervous  system. 
9 


CHAPTER   IV. 
BACTERIOLOGY  AND  STERILIZATION. 

By  L.  F.  RETTGER,  Ph.D. 

For  many  years  it  was  thought  that  insofar  as  the  body  was  con- 
cerned bacteria  were  necessary  to  its  welfare;  that  they  helped  it  in 
some  way.  It  was  even  thought,  by  many  at  least,  that  life  was 
maintained  h)y  the  very  existence  of  bacteria  within  the  body. 

For  example,  it  was  taught  that  some  of  the  intestinal  bacteria 
were  necessary  for  certain  processes  that  go  on  in  the  intestine;  that 
intestinal  digestion  was  not  complete  without  bacteria.  The  problem 
was  argued  pro  and  con  for  years  but  it  has  been  well  demonstrated 
that  the  old  view  was  an  erroneous  one. 

Yet,  while  the  bacteria  that  are  present  in  the  body  are  not  neces- 
sarily helpful,  there  are  organisms  in  nature  which  do  aid  in  an  eco- 
nomic way,  such  as  those  which  are  of  special  importance  in  connection 
with  the  growing  of  plants.  Some  farm  products  depend  in  a  large 
measure  on  bacteria.  So  that,  in  spite  of  what  is  said  as  to  the  prob- 
ability that  bacteria  are  useless  within  the  body,  we  owe  much  to  them 
because  of  this  external  cooperation. 

Ordinarily  the  bacteria  within  the  body  are  harmless.  Normally 
they  are  unable  to  overcome  its  natural  resistance.  Fortunately  it  is 
against  only  a  few  kinds  of  bacteria  that  the  body  is  compelled 
constantly  to  protect  itself.  The  fight  against  these  of  course  consti- 
tutes one  phase  of  hygiene  and  a  most  interesting  and  important  one. 

The  practice  of  this  phase  of  hygiene  falls  within  the  modern  con- 
ception of  medicine;  to  prevent  bacteria  or  other  harmful  agencies 
from  getting  a  foothold  and  working  mischief,  rather  than  to  try  to 
eliminate  them  after  they  once  establish  themselves  should  be  the 
chief  aim  of  science.  A  few  years  ago  ex-president  Eliot  of  Harvard 
said  that  the  real  medical  school  of  the  future  was  the  school  of  pre- 
ventive medicine.  Modern  dentistry,  like  medical  science,  is  likewise 
moving  in  that  direction.  This  is  due  to  the  fact  that  men  who  are 
active  in  the  practice  of  these  professi(jns  now  realize  that  they  will 
accomplish  the  greatest  good  if  they  direct  their  energies  toward  the 
prevention  rather  than  the  cure  of  disease. 

There  are  many  diseases  that  are  now  known  to  be  caused  by 
bacteria,  such  as  typhoid  fever,  tuberculosis,  diphtheria,  and  a  large 
number  of  others,  the  specific  causes  of  which  are  well  recognized. 
(Combating  typhoid  fever  means,  in  reality,  keeping  out  of  the  way  of 
the  bacterium  which  causes  it.     In  the   present-day  fight  against 


Fig.  42. — Tuberculous   sputum  stained  by  Gabbett's  method.      Tubercle  bacteria  seen 
as  red  rods;  all  else  is  stained  blue.     (Abbott.) 


CLASSIFICATION  OF  BACTERIA  131 

tuberculosis  au  outleavor  is  made  to  keep  out  of  the  way  of  the  tubercle 
bacillus.  Since  there  are  so  many  chances  of  getting  into  trouble  with 
foreign  harmful  agencies  like  bacteria,  it  is  important  to  know  some- 
thing about  them. 

Description  of  Bacteria. — Some  of  the  largest  bacteria  measure  ^o^^^a 
of  an  inch  in  thickness,  or,  in  other  words,  it  takes  25,000  of  them 
packed  closely  side  l)y  side  to  cover  an  inch.  This  gives  a  vague  con- 
ception of  the  minuteness  of  these  organisms.  In  order  that  they  may 
be  examined  it  is  necessary  to  use  the  best  and  most  ]K)werful  micro- 
scope to  bring  them  to  view.  From  this  it  can  readily  be  understood 
that  years  of  scientific  study  have  been  required  to  glean  any  real 
knowledge  concerning  them. 

Bacteria  are  vegetable  organisms,  not  animal.  Therefore  it  is  wrong 
to  call  them  bugs,  worms,  or  anything  inferring  a  close  relationship 
to  that  kingdom. 

A  bacterium  is  essentially  a  minute  mass  of  protoplasm  surrounded 
by  a  delicate  envelope.  This  protoplasm  is  the  same  in  bacteria  as  in 
all  other  living  cells,  and  is  peculiar  to  living  matter. 

Bacteria  are  single-celled  organisms.  They  may  often  occur  in 
bunches  or  chains,  but  their  unit  is  the  single  cell;  so  that  each 
individual  bacterium  is  able  to  reproduce  its  kind. 

CLASSIFICATION  OF  BACTERIA. 

The  protoplasm  of  the  bacterial  cells  is  held  in  shape  by  a  delicate 
envelope,  or  defining  wall;  consecj[uently  bacteria  can  be  regarded  as 
being  definite  in  size  and  in  shape. 


Fig.  43. — Staphylococcus.      X  1100  diameters.     (Park.) 

In  a  large  measure,  the  size,  shape,  internal  structure  and  grouping 
of  the  different  organisms  are  used  as  means  of  recognizing  and 
classifying  them.  The  tubercle  bacillus  is  spoken  of  as  being  a  long, 
slender  bacillus  (very  long  as  compared  with  its  thickness),  and  this 
fact  is  depended  upon,  to  a  large  extent  for  diagnostic  purposes,  that 
is,  for  the  detection  of  the  tubercle  bacillus  in  any  part  of  the  body 


132 


BACTERIOLOGY  AND  STERILIZATION 


that  may  possibly  be  infected  with  tuberculosis  (Fig.  42).  The  same 
thing  is  true  insofar  as  the  typhoid  bacillus  is  concerned.  The  com- 
mon pus  organisms  that  occur  so  frequently  in  the  mouth,  especially 
in  abscesses  of  the  gums  and  in  a])scesses  in  other  parts  of  the  body 
represent  a  different  type.  They  are  organisms  which  are  round  or 
almost  globular  (Fig.  43). 


■j^riS.tfc 


Fig.  44. — Spirillum  obermeieri  blood-smear.     Fuchsin.      X  1000  diameters. 
(From  Itzerott  and  Niemann.) 

There  is  a  third  type  of  organism  which  is  often  present  in  the 
mouth.  It  is  also  frequently  found  in  stagnant  water,  and  in  infusions 
of  hay,  straw,  etc.  These  are  rod-shaped  like  the  typhoid  bacillus, 
but  the  rods  are  decidedly  curved  and  longer;  they  resemble  a  spiral 
(Fig.  44). 

We  have  then,  first,  the  simple,  straight,  rod-shaped  organism  called 
the  bacillus  (Fig.  42) ;  second,  the  globular  type,  known  as  coccus,  or 
micrococcus  (plural  cocci,  Fig.  43) ;  and  third,  the  long,  slender,  curved 
rod,  known  as  the  spirillum  (Fig.  44,  plural  spirilla). 


PROPAGATION  OF  BACTERIA. 

How  do  these  organisms  propagate  their  own  kind?  In  brief,  bac- 
teria multiply  by  a  process  of  transverse  division.  A  large  bacillus, 
for  example,  when  it  has  reached  full  maturity,  divides  into  halves. 
The  process  is  simply  one  of  equatorial  fission,  or  of  separation  of  the 
halves  by  a  little  dividing  wall  which  becomes  more  and  more  apparent 
until  the  constriction  becomes  complete,  and  instead  of  one  parent 
cell  two  slaughter  cells  appear.  '^I'his  is  in  reality  the  only  method  of 
multiplication.  Spore  formation^  which  is  referred  to  later,  does  not 
constitute  a  state  or  stage  of  reproduction  in  the  real  sense  of  the  word. 

'J'he  abo\e  method  is  also  sj)oken  of  as  the  economic  process  because 
of  the  grc;it  raj)idity  with  which  multiplication  takes  ])lace.  A  bottle 
of  milk  will  sour  in  the  course  of  a  few  hours  if  ke])t  at  a  moderately 
warm  temperature.     The  milk  spoils  because  it  is  such  a  good  food 


SPORE  FORMATION  133 

for  certain  bacteria,  known  as  the  lactic  acid  organisms,  that  multij^ly 
rapidly. 

Milk  sDtir.s.  Other  foods,  like  meats,  do  not  sour;  they  decay,  and 
by  an  entirely  difi'crent  process;  the  decay  of  meat  is  ordinarily  spoken 
of  as  piitrcfartio)!.  But  in  either  case  the  food  is  there,  the  bacteria 
are  there,  deconij)()siti()n  occurs,  and  in  the  process  of  this  decomposi- 
tion the  bacteria  have  l)een  multiplying  rapidly. 

It  can  be  determined  readily  how  rapidly  these  organisms  reproduce 
themselves.  Start  with  one  organism,  allow  it  to  go  on  reproducing 
its  kind  at  the  rate  of  one  reproduction  an  hour,  that  is,  the  doubling 
of  the  original  bacillus  and  the  doubling  of  each  of  its  progeny  once 
every  hour,  and  there  will  be  in  twenty-four  hours  over  1  (5,000,000 
of  them.  If  the  reproduction  occurs  once  in  thirty  minutes,  it  will  be 
necessary  to  use  higher  mathematics  to  compute  the  number  at  the 
end  of  twenty-four  hours,  and  frequently  in  a  new  mediimi  like  milk 
or  beef  broth  which  is  prepared  for  such  a  purpose,  reproduction  does 
occur  as  often  as  once  in  thirty  minutes.  In  some  cases  complete 
division  may  occur  in  twenty  minutes.  Thus  it  may  be  seen  how  the 
term  rcononn'r  rnefhod  of  multiplication  applies. 

Spore  Formation. — There  are  many  kinds  of  bacteria  that  have  the 
property  of  being  able  to  fortify  themselves  against  destructive  agents. 
This  is  accomplished  by  virtue  of  their  ability  to  take  on  a  form  that 
is  much  more  resistant  to  injury  than  the  normal  state  of  the  organ- 
ism. They  can  change  themselves  into  what  are  termed  spores. 
The  tetanus  or  lockjaw  bacillus  has  this  propertv,  for  example. 
(Fig.  45.) 


Fk;.  45. — Tetanus  bacilli  with  spores  in  distended   ends.       X   1100  diameters.      (Park.) 

A  spore  then  is  a  transition  form  that  certain  bacteria  can  assume 
for  purposes  of  defense. 

Spores  possess  a  thick  wall,  which  is  more  or  less  impervious  to 
heat,  poisons,  etc.,  and  therefore  protects  the  contents  against  fatal 
injury.  In  this  way  spore-producing  organisms  can  fortify  themselves 
against  destructive  influences  which  ordinary  bacteria  may  be  unable 
to  resist.     Spores  remain  dormant  as  long  as  conditions  for  growth 


134 


BACTERIOLOGY  AND  STERILIZATION 


and  development  are  unfavorable.  When,  however,  new  food  is  sup- 
plied, and  harmful  influences  have  been  removed,  they  develop  into 
the  original  types  of  bacteria  which  gave  rise  to  them  by  a  simple 
process  which  may  be  called  germination. 

The  importance  oj  the  spore,  or  spore-production  by  bacteria,  cannot 
be  overestimated.  If  it  were  not  for  the  spore  it  would  be  very  easy 
to  sterilize  objects.  Fortunately,  however,  comparatively  few  disease- 
producing  bacteria  have  the  property  of  producing  spores. 

ARTIFICIAL  CULTIVATION  OF  BACTERIA. 

There  are  various  ways  of  growing  bacteria.  Some  favorable 
nutrient  medium  must  be  employed  like  milk,  beef  broth,  and  nutrient 
gelatin  or  jelly. 

The  examination  of  a  specimen  of  milk  or  water  is  accomplished  by 
putting  a  drop  or  several  drops  in  a  tube  of  jelly  that  has  been  warmed 
enough  to  liquefy  it,  mixing  the  contents  well  and  then  pouring  it 
into  little  glass  plates  made  for  this  purpose  (Petri  xlishes).  By  this 
procedure  it  is  possible  to  get  the  bacteria  away  from  the  milk  or 


Fici.  40. — Anthrax  bardlli. 


water  and  start  them  growing  in  the  new  medium.  The  jelly  hardens 
just  as  ordinary  table  jelly  does.  After  one,  two  or  three  days  quite 
a  change  will  have  taken  place  in  the  jelly;  the  same  sort  of  change 
that  frccpiently  takes  place  on  a  slice  of  bread  that  is  put  into  the 
bread-box  when  dajnp;  the  same  sort  of  change  that  takes  place  on  a 
bit  of  cooked  potato  that  is  kept  long  enough.  Families  of  bacteria 
have  grown  here  and  there,  forming  various  sized  masses.  These 
families  are  the  offspring  of  the  individual  })a('teria  that  were  in  the 
drop  of  milk  or  water  which  was  placed  in  the  liquefied  jelly.     Such 


ARTIFICIAL  CULTIVATION  OF  BACTERIA 


135 


families  or  "jroiips  may  frequently  be  distinguished  from  eaeh  other  by 
their  famil\'  traits.    These  families  are  known  as  cohmics. 

Frequently  the  mieroscope  is  used  to  examine  the  colonies  as  well 
as  the  individual  organisms.  As  a  rule  each  colony  is  the  product 
of  one  original  bacillus,  spirillum,  or  micrococcus. 


Fig.  47. — Typhoid  Ijafilli  from  mitiient  gelatin.      X  1100  diameters.      (Park.) 

In  studying  a  plate  containing  a  number  of  colonies  of  different 
bacteria  a  great  variation  in  their  character  will  be  noted.  Some  are 
large,  others  small;  some  are  colored,  others  colorless,  etc.  In  other 
words,  they  show  dift'erent  family  traits.  The  differentiation  of  family 
characteristics  plays  an  important  part  in  the  process  of  identification 
and  is  used  for  diagnostic  purposes. 


Fig.  48. — Streptococci  in  peritoneal  fluid,  partly  enclosed  in  leukocj'tes. 
X  1000  diameters.      (Parlv.) 


Often  the  investigation  is  carried  still  further  by  various  methods. 
For  instance,  one  -or  more  of  these  colonies  may  be  further  isolated; 
some  of  the  individual  bacteria  may  be  removed  from  these  colonies 
and  placed  in  a  tube  of  sterile  jelly,  milk  or  broth.  The  tube  is  then 
closed  with  an  ordinary  cotton  plug,  and  put  away  for  development. 
The  organisms  are  now  isolated  or  imprisoned,  and  may  be  held 
indefinitely  under  these  conditions.    Why  is  all  this  necessary?    Just 


136  BACTERIOLOGY  AND  STERILIZATION 

as  soon  as  one  bacterium  is  isolated  from  another  and  studied,  the 
danger  of  confusion  is  avoided.  It  is  impossible  to  study  any  par- 
ticular kind  of  organism  to  the  best  advantage  when  another  organism 
is  present.  Different  organisms  produce,  as  a  rule,  different  kinds 
of  growth  on  the  surface  of  sloped  jelly  or  agar.  In  some  instances  the 
growth  is  scanty,  in  others,  luxuriant.  Some  growths  are  raised,  rough  or 
irregular;  others  are  smooth,  flat  and  regular.  The  common  organism 
known  as  Bacillus  prodigiosus  produces  a  blood-red  color;  another, 
the  most  common  pus  organism,  a  golden-yellow  pigment;  some, 
like  the  typhoid  bacillus,  produce  no  color  at  all. 


¥u:.  49. — Piieumococc!. 

A  microscopic  examination  of  the  bacteria  present  in  a  colony 
furnishes  additional  information.  This  is  accomplished  by  removing 
a  small  portion  of  the  growth  and  spreading  it  on  a  microscopic  slide 
in  a  dro]j  of  water.  Some  kinds  of  bacteria  will  be  seen  to  swim  about 
of  their  own  accord.  The  property  of  moving  about  independently 
in  a  liquid,  which  some  bacteria  possess,  is  termed  motility.  They 
have  moving  organs  known  as  'flaf/eUa.  A  large  number  of  bacteria 
can  mo\'e  about  iiidejx'iidently.  On  the  other  hand,  a  large  grou]) 
lack  this  i)roi)erty;  they  are  iion-iiioiilc;  they  do  not  have  flagella.  In 
addition  to  motility,  the  si'/e,  shape  and  other  iiiicn)sc()])ic  characters 
are  studied. 

While  organisms  are  grouped  under  the  three  types  previously  men- 
tioned, members  of  each  gronj)  \vd\v  (listingnishing  characteristics  of 
their  own,  differing  in  appearance  as  individuals,  and  so  permitting 
flefinite  recognition  or  diagnosis  under  the  eye  of  the  microscope.    To 


BACTERIA    IN   THEIR  RELATION   TO  DISEASE  137 

make  this  clear  it  is  but  necessary  to  study  the  accompan\iii,<!;  ilhis- 
tratious  which  show  some  of  the  famihar  bacteria. 

Fig.  46  is  a  picture  of  the  anthrax  bacillus.  Note  that  these  organisms 
are  large  and  tend  to  group  themselves  into  chain-like  formations. 
Compare  them  with  the  tubercle  bacillus  (Fig.  42.) 

Fig.  47  shows  the  typhoid  Inicillus.  Notice  the  difl'erences  in  the 
length  of  the  baciUi.  Some  are  quite  short,  others  long;  the  thickness 
is,  however,  uniform.  The  typhoid  bacillus  is  very  small  compared 
with  the  anthrax  organism ;  also,  it  differs  in  the  method  of  grouping, 
the  typhoid  bacillus  being,  as  a  rule,  single,  not  paired  or  in  chains. 

Fig.  48  illustrates  one  of  the  pus-producing  organisms.  This  is  a 
coccus  and  tends  to  gather  in  chain-like  formations. 

F'ig.  49  shows  another  coccus.  This  is  the  diplococcus  of  pneu- 
monia, called  diplococcus  because  it  occurs  in  pairs.  Aside  from  this 
peculiarity,  this  organism  is  surrounded  by  a  peculiar  halo-like  structure, 
known  as  a  capsule.     The  large  round  objects  are  blood  cells. 


Fig.  50. — One  of  the  ven,'  characteristic  forms  of  diphtheria  bacilli  from  blood-scrum 
cultures,  showing  clubbed  ends.      X  1100  diameters      (.Simon.) 

Fig.  50  is  a  picture  of  the  diphtheria  bacillus  in  pure  culture. 
The  illustration  shows  its  peculiar,  irregular,  and  more  or  less  granular, 
club-shaped  form. 

So  it  is  obvious  that  these  organisms  all  differ  and  may  be  readily 
di.stinguished  from  each  other  by  one  who  is  familiar  with  them. 


BACTERIA  IN  THEIR  RELATION  TO  DISEASE. 

Most  organisms  encountered  in  nature  are  of  the  harmless  kind. 
Scientificially  they  are  known  as  the  non-pathogens,  or  the  non-patho- 
genic bacteria.  The  non-pathogenic  bacteria  occur  very  abundantly 
in  nature.  There  are  endless  varieties  of  them.  They  are  found  in 
the  air,  in  water,  in  the  soil,  on  the  skin,  in  the  mouth,  and  in  the 
entire  digestive  tract.  Little  attention  need  be  paid  ordinarily  to  the 
non-pathogens  insofar  as  disease  production  is  concerned. 

Certain   diseases   are   brought   about    by   specific   bacteria   which 


138  BACTERIOLOGY  AND  STERILIZATION' 

constitute  a  comparatively  small  group  of  microorganisms  and  are 
known  as  the  pathogenic  bacteria,  or  yathogens.  By  the  pathogenic 
bacteria  are  meant  bacteria  which  are  able  to  enter  the  body,  to 
multiply  and  set  up  disturbances;  in  other  words,  to  produce  disease. 
This,  then,  is  the  chief  distinction  to  be  made  between  non-pathogens 
and  pathogens,  viz.,  non-pathogens  are  ordinarily  harmless;  pathogens 
are  disease  producers. 

Pathogenic  bacteria  are  organisms  which  in  the  usual  laboratory 
tests  appear  exactly  like  the  non-pathogenic.  The  only  essential 
difference  lies  in  the  peculiar  action  of  the  pathogens  when  introduced 
into  susceptible  hosts.  Some  of  the  pathogens  may  be  isolated  in  the 
manner  previously  described  and  then  may  be  studied  in  their  various 
relationships.  The  most  significant  thing  about  them,  however,  is 
the  effect  that  such  pathogens  have  on  the  host  which  they 
invade. 

The  production  of  disease  hy  bacteria  depends  upon  two  things: 
(a)  on  the  invading  organism,  and  (b)  on  the  relative  susceptibility 
or  immunity  of  the  host. 

(a)  The  Invading  Organism. — The  ability  of  invading  organisms  to 
produce  disease  also  depends  upon  tw^o  things:  First,  their  virulence. 
By  virulence  is  meant  their  ability  to  produce  disturbances  when  the 
conditions  of  the  host  are  such  as  to  permit  it.  Virulence  determines 
in  a  large  measure  whether  the  typhoid  bacillus  is  going  to  produce 
typhoid  fever  when  it  enters  the  digestive  system.  Second,  whether 
any  organism  in  question  is  going  to  produce  disease  or  not  also 
depends  on  its  numbers.  Years  ago  it  was  thought  that  one  tubercle 
bacillus  was  sufficient  to  produce  tuberculosis,  or  that  one  typhoid 
bacillus  was  enough  to  start  typhoid  fever;  but  the  opinion  regarding 
that  point  has  decidedly  changed.  An  organism  that  is  extremely 
powerful  or  very  virulent,  or  an  organism  that  is  specially  well 
endowed  with  the  property  of  producing  its  own  particular  kind  of 
disturbance  in  a  very  susceptible  host,  can  do  its  work  in  comparatively 
small  numbers.  In  fact,  the  white  mouse  and  the  guinea-pig  are  so 
susceptible  to  tuberculosis  that  it  is  claimed  one  tubercle  bacillus  may 
produce  tuberculosis  when  experimentally  introduced.  On  the  other 
hand,  calves  are  not  affected  seriously  by  tubercle  bacilli  unless  these 
are  exceedingly  virulent  and  of  the  bovine  type  of  bacilli. 

ib)  The  SvscejjtibiJity  of  the  Host. — Man  is  susceptible  as  a  race  to 
typhoid  fe\er.  All  animals,  so  far  as  we  know,  are  immune.  On  the 
other  hand,  the  tubercle  bacillus  is  pathogenic  in  the  full  sense  of  the 
word.  There  are  apparently  few  species  of  vertebrate  animals  which 
are  not  susceptible  to  some  form  of  tuberculosis.  Even  cold-blooded 
animals,  like  turtles  and  fish,  are  said  to  be  victims. 

How  a  Pathogen  Acts. — When  a  pathogen  succeeds  in  bringing  about 
bacterial  disturbances,  it  does  so  in  two  ways:  First,  it  multiplies  in 
the  body;  second,  in  the  light  of  more  recent  knowledge  it  produces 
poisons  or  toxins.     It  is  said  that  the  pathogen  differs  essentially  from 


BACTERIA   IN   THEIR  RELATION   TO  DISEASE  139 

the  non-pathogen  in  that  the  former  is  a})le  to  produee  toxins,  while 
the  latter  is  not.  However,  in  order  that  the  pathogen  may  produce 
appreciable  amounts  of  poisons  or  toxins  in  the  human  body  it  must 
first  establish  itself.  For  example,  the  diphtheria  bacillus  when  it 
enters  the  mouth  and  throat  or  nose,  sets  up  local  disturbances  there. 
It  does  not  enter  the  blood,  except  in  very  rare  instances.  It  multiplies 
locally  usually  in  the  throat  and  yet  the  symptoms  of  diphtheria  are 
not  confined  to  the  throat.  In  diphtheria  the  impprtant  effects  are 
those  of  general  poisoning.  There  is  nervous  disorder,  fever,  ema- 
ciation, etc.,  which  cannot  be  explained  on  any  other  ground  except 
that  the  diphtheria  bacillus  produces  some  sort  of  a  poison  which  is 
distributed  generally  throughout  the  body,  and  which  itself  is  directly 
responsible  for  the  disease  complex. 

The  same  thing  may  be  said  with  reference  to  lockjaw.  There  is 
only  a  local  injury,  probably  brought  about  by  a  rusty  nail  or  by  an 
ordinary  wooden  splinter.  If  infection  takes  place,  it  is  confined  to 
the  seat  of  injury,  but  this  local  swelling,  inflammation  and  pain  are 
of  minor  significance.  The  important  factor  is  the  poisoning  of  the 
system  by  the  toxins  which  are  produced  locally  either  in  the  finger, 
the  hand,  the  foot  or  elsewhere.  It  is  the  action  of  these  poisons  that 
are  sent  out  from  this  local  infection  throughout  the  body,  affecting 
the  heart,  the  nerve  centers  and  other  organs,  that  is  so  frequently 
fatal. 

Peculiar  preventive  measures  have  been  evolved  against  diphtheria 
and  lockjaw.  These  are  to  a  certain  extent  even  curative  in  action. 
The  preventive  agents  are  known  as  antitoxins.  In  diphtheria  and  in 
lockjaw  infection  there  are  produced  what  are  known  as  extracellular 
poisons  or  toxins.  This  fact  has  been  demonstrated  clearly,  for  the 
toxins  have  been  produced  under  artificial  conditions  in  ordinary  beef 
broth,  etc. 

Paths  of  Infection. — When  a  bacterial  disease  is  produced  the  organ- 
ism must  have  access  to  the  part  of  the  body  that  is  immediately 
affected.  The  avenues  by  which  the  organism  gains  its  entrance  are 
known  as  paths  or  channels  of  infection.  For  instance,  in  diphtheria  the 
paths  of  infection  are  the  mouth  and  nose.  Of  these  the  mouth  is 
by  far  the  more  important.  In  lockjaw  the  path  of  infection  is  usually 
the  skin.  The  lockjaw  bacillus  enters  through  a  broken  or  ruptured 
portion  of  the  protecting  tissue  of  the  body.  In  typhoid  fever  the 
mouth,  gullet,  stomach  and  intestine  constitute  the  path  of  infection. 
Knowing  what  the  particular  cause  of  any  disease  is  and  also  the  paths 
of  infection,  make  it  possible  to  combat  this  disease  with  some  con- 
siderable degree  of  success. 

The  history  of  cholera  may  be  taken  as  a  good  illustration  of  the 
value  of  such  knowledge.  Ever  since  1883  it  has  been  known  that 
cholera  is  produced  by  a  disease-producing  organism  termed  the 
cholera  spirillum  or  cholera  comma  bacilhis,  so  named  because 
at  times  it  looks  like  an  ordinarv  comma  under  the  microscope,  and 


140  BACTERIOLOGY  AND  STERILIZATION 

sometimes  like  a  spiral.  It  is  well  known  that  the  seat  of  infection  is 
the  intestine.  An  organism,  then,  to  produce  Asiatic  cholera  must  be 
the  Asiatic  cholera  organism,  and  it  must  have  access  to  the  intestine 
through  the  mouth,  gullet,  and  stomach.  What  is  the  result  of  the 
knowledge  of  these  facts  alone  ?    The  following  will  clearly  demonstrate : 

Before  the  discovery  of  the  cholera  organism  Europe  and  America 
were  visited  almost  periodically  by  cholera  epidemics.  These  epidemics 
have,  as  a  rule,  had  their  origin  in  India.  In  fact,  it  may  be  said 
that  India  is  the  home  of  Asiatic  cholera.  It  exists  there  year  in  and 
year  out.  At  certain  times  it  breaks  out  in  severe  epidemic  form,  and 
in  some  of  the  great  epidemics  hundreds  of  thousands  of  Hindoos  have 
fallen  prey  to  the  disease.  In  their  various  religious  pilgrimages  they 
naturally  carry  infection  with  them  from  place  to  place,  and  thus 
produce  new  centers  of  distribution.  It  is  but  natural  that  cholera 
should  follow  routes  of  travel  and  in  this  way  become  general  unless 
effective  preventive  measures  are  employed. 

Cholera  has  spread  again  and  again  from  India  through  the  rest  of 
Asia  and  to  Europe;  it  has  also  periodically  invaded  America. 
Some  visitations  have  been  very  serious.  The  last  cholera  epidemic 
in  North  America  was  in  1870  and  1871.  Practically  nothing  was 
known  about  cholera  then,  aside  from  its  telling  effect.  In  the  last 
epidemic,  the  national  authorities  made  a  very  strenuous  effort  to 
cope  satisfactorily  with  the  situation.  They  strengthened  their  vigi- 
lance at  the  ports  where  European  ships  entered;  they  improved 
their  system  of  cholera  prevention  in  general;  but  even  then  health 
officers  were  practically  helpless  until  they  acquired  the  information 
that  cholera  is  caused  by  only  one  particular  kind  of  organism,  that 
this  organism  establishes  itself  in  the  intestine  and  there  does  its 
injurious  work. 

A  few  years  ago  Russia  was  visited  by  one  of  these  epidemics. 
The  disease  spread  through  Moscow,  through  St.  Petersburg,  and  in 
fact  lingered  on  the  borders  of  Russia  for  two  years  or  more.  Hundreds 
of  cholera  victims  died  daily  in  some  of  the  large  cities-,  (xermany 
was  constantly  on  the  lookout  for  the  imported  cholera  cases.  The 
border  was  carefully  patrolled  on  the  Russian  side.  Not  only  that, 
but  every  person  entering  Germany  who  excited  the  least  suspicion 
as  to  being  a  cholera  carrier  was  followed  to  his  destination  and  put 
under  severe  scrutiny  by  the  officials.  In  spite  of  this  vigilance  there 
were  at  least  one  hundred  isolated  cases  of  cholera  in  (Jermany.  These 
cases  were  distributed  throughout  (lermany.  They  were  cases  that 
were  introduced  mainly  from  Russia,  but  they  renuiined  individual 
isolated  cases  and  did  not  spread  the  disease. 

All  sorts  of  laboratory  tests  have  been  made  in  (icrmany  and  in 
our  own  laboratories  in  New  York,  in  order  to  prevent  persons  from 
actually  entering  and  taking  up  their  abode  in  this  country  who  were 
not  only  infected  with  cholera  but  were  what  we  call  cholera  carriers. 
They  even  went  so  far  in  New  York  as  to  make  individual  examinations 


BACTERIA   IN    THEIR  RELATION   TO  DISEASE  141 

of  all  steerage  pasengers  on  steamships  coming  from  cholera-infected 
foreign  ports.  That  was  the  end  of  the  introduction  of  even  sporadic 
cases  of  cholera  into  the  United  vStates. 

Here,  then,  is  a  good  illustration  of  what  the  disco  very  of  the  particular 
pathogen  and  the  determination  of  the  path  of  infection  through  which 
that  pathogen  must  travel  in  order  to  set  up  its  disturbance  and 
produce  the  disease  in  question  will  do  from  the  standpoint  of  pre\en- 
tion.  And  this  same  principle  applies  generally.  For  example,  the 
plague,  \vhich  has  been  so  common  in  Inflia,  China,  Japan  and  the 
Philippines,  is  another  illustration.  In  the  past  there  have  been  large 
epidemics  of  plague  in  those  countries.  Even  San  Francisco  was 
plague-ridden  several  years  ago. 

In  the  last  ten  or  fifteen  years  we  have  come  to  feel  as  secure  in  this 
country  against  plague  as  against  Asiatic  cholera.  Such  a  feeling 
of  security  did  not  exist  twenty-five  years  ago,  because  at  that  time 
little  or  nothing  was  known  about  the  plague  bacillus,  and  of  the 
methods  by  which  it  could  pass  from  one  individual  to  another  and 
produce  plague. 

When  it  was  determined  that  plague  may  be  transmitted  from 
man  to  man  through  the  agency  of  the  rat  and  the  rat  flea,  a  great 
forward  step  was  made.  Rats  are  a  severe  menace  in  any  community 
which  is  threatened  with  an  invasion  of  bubonic  plague.  One  may  ask 
how  rats  in  themselves  can  be  a  menace.  Rats  are  naturally  infected 
with  fleas,  and  it  has  been  shown  by  actual  experiment  in  India  and  else- 
where that  these  fleas  pass  not  only  from  one  rat  to  another,  but  they 
may  pass  from  rat  to  man.  It  has  also  been  shown  experimentally 
that  a  rat  flea  which  has  left  a  rat  infected  wdth  bubonic  plague, 
when  it  bites  another  animal,  is  likely  to  introduce  the  germ  of  bubonic 
plague  with  the  act  of  biting.  This  knowledge  has  done  a  great  deal 
to  solve  the  problem  of  plague  prevention. 

Comparatively  recently  another  big  chapter  was  added  to  the  history 
of  plague  prevention.  There  was  a  recent  epidemic  of  plague  in 
Manchuria.  Previous  to  this  it  was  believed  that  rats  and  rat  fleas 
alone  played  the  important  part  in  the  transmission  of  this  disease. 
Howe\'er,  it  was  demonstrated  clearly  that  in  Manchuria  the  rat  did  not 
play  much  of  a  part,  but  that  the  plague  there  was  of  a  peculiar 
pulmonary  type,  very  much  like  ordinary  consumption;  that  the 
plague  bacillus  was  spread,  not  through  the  rat,  but  from  person  to 
person  by  ordinary  coughing  or  talking.  Acting  in  accordance  with 
this  important  information  the  medical  authorities  soon  rid  ^lanchuria 
of  its  epidemic.  Physicians  and  nurses  who  attended  the  patients 
remained,  with  very  few  exceptions,  absolutely  free  from  the  disease, 
by  guarding  themselves  against  infection  with  the  aid  of  face  masks, 
long  coats,  etc. 

The  Mouth  as  a  Path  of  Infection. — Many,  and  perhaps  most,  of  the 
organisms  that  are  now  known  to  be  the  real  causes  of  disease  are 
eliminated  through  the  mouth  or  intestine,  and  enter  the  future  victim 


142  BACTERIOLOGY  AND  STERILIZATION 

through  the  mouth  as  the  important  channel.  Following  are  some 
significant  examples. 

In  diphtheria  the  organism  has  as  the  path  of  infection  the  mouth, 
nose,  and  the  throat.  In  tuberculosis  the  channel  of  infection  is  the 
mouth,  windpipe,  and  the  lungs,  or  the  mouth  and  digestive  tract. 
In  follicular  and  other  presumably  infectious  types  of  tonsillitis  it  is 
apparently  the  mouth.  In  the  epidemics  of  milk-borne  sore  throats 
that  have  occurred  in  Boston,  Baltimore,  Chicago,  and  other  cities, 
in  the  last  few  years,  the  channel  of  infection  was  the  mouth.  In 
dysentery,  and  in  pulmonary  plague,  are  found  additional  illustrations. 
Many  authorities  claim  that  the  organism  of  smallpox  probably 
enters  through  the  mouth  or  nose.  The  same  idea  is  held  by  some  with 
regard  to  measles  and  mumps.  Whooping-cough  and  influenza  fall 
in  this  category.  There  are  very  few  of  the  well-known  infectious 
diseases  that  are  not  brought  about  by  the  entrance  of  the  organism 
through  the  mouth,  or  the  mouth  and  nose. 

This  of  course  is  of  special  significance  in  the  work  of  the  dental 
hygienist,  for  a  clean  mouth  necessarily  means  a  lessened  danger  of 
infection  through  that  channel. 

Tuberculosis  may  be  produced  by  breathing  the  tubercle  bacillus, 
or  it  may  be  produced,  as  many  claim,  as  the  result  of  swallowing  the 
tubercle  bacillus,  as  in  milk. 

The  fact  that  tuberculosis  of  children  is  often  associated  with 
the  intestine  has  brought  forth  the  theory  that  milk-borne  tuber- 
culosis is  a  not  uncommon  thing;  that  tuberculosis,  particularly  in 
the  child,  may  be  brought  about  by  the  use  of  milk  from  tuberculous 
cows.  If  this  is  true,  man  is  susceptible  not  only  to  the  human  type 
of  tuberculosis,  but  to  bovine  as  well,  and  may  contract  tuberculosis 
through  at  least  two  different  channels  of  infection,  namely,  the  mouth 
and  the  trachea  on  the  one  hand,  and  the  mouth  and  the  digestive  tract 
on  the  other. 

All  of  these  eft'orts  to  stufly  the  various  diseases  from  the  standpoint 
of  prevention  have  resulted  in  at  least  partial  success. 

BACTERIOLOGY  AND  HYGIENE. 

It  is  rather  difficult  to  divorce  the  subject  of  bacteria  from  hygiene, 
and  the  relation  of  bacteriology  to  public  hygiene  is  of  great  interest. 
In  this  connection  a  few  figures  regarding  the  diphtheria  death-rate 
in  Prussia  in  187()  as  compared  with  1909  are  convincing.  In  187G  the 
death-rate  was  \().'4  per  10,000  as  compared  with  2.5  in  1909.  The 
tuberculosis  figures  are  as  follows:  In  1876  the  death-rate  for  Prussia 
was  30  per  10,000,  while  in  1909  it  was  only  1(1,  a  reduction  of  about 
one-half.  In  ^Massachusetts  the  figures  compare  quite  favorably 
with  those  just  mentioned.  Snch  figures  are  most  gratifying.  It  was 
in  1883  that  Koch  made  his  famous  discovery  of  the  tubercle  bacillus, 
and  from  that  time  on  the  main  emphasis  in  prevention  was  directed 


FERMENTS  143 

in  such  a  way  as  to  combat  the  tubercle  baciUus  and  prevent  its  spread 
from  person  to  person,  which  accounts  in  a  large  measure  for  the 
remarkable  progress  that  has  been  made. 

One  prominent  English  authority  said  a  few  years  ago  that  if  the 
decrease  in  tuberculosis  continued  for  fifty  years  as  it  had  done  for  the 
past  ten  or  fifteen,  that  tuberculosis  would  be  completely  wiped  out. 
The  numerous  health  resorts,  tuberculosis  sanitoriums,  various 
methods  of  dieting,  exercise,  medical  examination,  etc.,  all  have  had 
their  telling  effect. 

It  is  claimed  that  in  our  own  country  the  death-rate  from  diphtheria 
has  been  reduced  fully  75  to  80  per  cent.  There  are  various  things 
that  contribute  to  this  enormous  reduction  of  the  death-rate  from 
diphtheria.  First  of  all,  there  was  the  discovery  of  the  diphtheria 
bacillus,  and  the  efficient  system  of  laboratory  diagnosis  of  the  disease. 
Diphtheria  and  tuberculosis  are  now  diagnosed  by  laboratory  methods 
in  all  cities  of  any  size  in  Europe  and  in  this  country.  Second,  the  use 
of  diphtheria  antitoxin.  This  has  played  an  immense  role  in  the 
lowering  of  the  death-rate  from  diphtheria.  Finally,  our  system  of 
quarantine,  which  has  grown  out  of  the  knowledge  that  diphtheria  is 
infectious  and  is  spread  from  mouth  to  mouth,  is  of  much  importance. 

In  the  field  of  malaria  prevention,  it  is  known  that  in  some  com- 
munities, particularly  in  the  Panama  Zone,  malaria  has  been  practically 
eradicated.  The  general  death-rate  among  our  laborers  in  Panama  is 
below  that  of  New  York.  When  the  Panama  railway  was  built  the 
main  obstacle  in  the  construction  of  that  railway,  and  also  at  various 
times  in  the  past  history  of  the  canal  enterprise,  was  the  prevalence 
of  deadly  tropical  diseases,  namely,  malaria  and  yellow  fever.  Yellow 
fever  is  practically  unheard  of  today  in  the  isthmus;  malaria  is  under 
-control. 

In  Cuba  yellow  fever  has  been  stamped  out.  For  a  number  of  years 
there  was  not  a  single  case  in  Havana.  That  was  soon  after  our  army 
commission  made  its  wonderful  study  of  the  problem  of  yellow  fever 
in  Cuba.  It  was  soon  after  their  demonstration  that  yellow  fever  was 
transmitted  from  mosquito  to  man;  or,  in  other  words,  that  yellow 
fever  required  as  an  intermediate  host  the  mosquito  known  as  the 
stegomyia,  or  yellow  fever  mosquito.  That  work  has  been  sub- 
stantiated, and  the  methods  of  prevention  of  yellow  fever  that  were 
put  into  effect  have  resulted  in  its  being  stamped  out  in  Cuba,  in  the 
Canal  Zone,  and  in  the  Gulf  States  where  a  few  years  ago  it  appeared 
and  assumed  threatening  proportions. 

FERMENTS. 

In  the  chapter  on  Physiology  organized  and  unorganized  ferments 
are  mentioned.  As  stated  there,  many  different  unorganized  ferments 
are  present  in  the  human  body.  They  are  known,  in  other  words, 
as  enzymes. 


1-H:  BACTERIOLOGY  AND  STERILIZATION 

The  unorganized  ferments,  or  enz^^■lles,  are  not  living  things.  They 
are  the  products  of  Hving  things.  On  the  other  hand,  the  organized 
ferments  are  living  things,  akhough  they  may  be  smgle-cehed. 

One  of  the  best  e.vamples  of  organized  ferments  is  ordinary  bread 
yeast,  or  beer  yeast;  they  are  very  much  ahke.  Of  course,  the  word 
■'ferment"  is  suggested  by  the  very  activities  of  the  ordinary  bread 
and  beer  yeasts.  These  are  characterized  in  their  real  activities  by 
the  fact  that  they  produce  alcohol  and  gas.  Beer  yeast  produces  con- 
siderable alcohol.  The  gas  is  known  as  carbonic  acid,  or  carbon  dioxid 
gas. 

It  has  been  known  for  some  time  that  the  food  substances  upon 
which  these  yeasts  act  are  chiefly  sugars  and  sugar-like  substances. 
]\Iost  of  the  yeasts  require  sugars,  such  as  malt  sugar,  or  grape  sugar. 
But  it  should  not  be  taken  for  granted  that  sugars  are  foods  for  yeasts 
only;  they  are  food  for  many  kinds  of  bacteria,  as  for  example,  some 
of  those  which  are  found  in  the  mouth  and  in  milk. 

In  beer  fermentation,  where  the  beer  yeasts  are  involved,  the  alcohol 
is  the  ordinary  alcohol  known  as  beer  or  wine  alcohol.  These  yeasts 
have  their  peculiar  process  of  multiplication,  namely,  that  of  budding. 
They  are  primarily  fermenting  organisms,  and  are  so  called  because 
they  produce  gas  and  alcohols  from  sugars.  There  are  a  large  number 
of  bacteria  that  will  ferment  just  as  the  yeasts  do.  Some  of  them  may 
be  bacteria  of  comparatively  large  size.  Some  are  more  or  less  closely 
related  to  and  have  certain  things  in  common  with  yeasts.  Then, 
again,  the  common  bacteria,  like  some  of  the  smallest  bacteria  of  the 
mouth,  the  ordinary  bacteria  in  milk,  or  the  milk-souring  bacteria, 
are  fermenting  organisms.  They  are  organized  ferments.  They  are 
agents  or  microorganisms  that  act  upon  sugar  as  well  as  other  food 
substances,  like  proteins.  Bacteria,  like  yeasts,  are  organized  ferments, 
in  distinction  from  ordinary  enzATues,  or  unorganized  ferments. 

FERMENTATION  AND  PUTREFACTION. 

Fermentation  and  putrefaction  are  produced  by  bacteria.  This 
means  that  bacteria  are  able  to  act  upon  various  kinds  of  food  sub- 
stances, splitting  them  up  into  many  components.  Some  bacteria 
will  split  these  food  substances  into  so  many  and  such  varied  parts 
that  the  complete  array  of  them  is  quite  surprising.  This  is 
particularly  true  of  the  so-called  putrefying  bacteria,  or  putrefiers, 
i.  e  ,  those  that  are  responsible  for  putrefacticm. 

Frequently  a  distinction  is  made  between  fermentation  and  jnitre- 
faction.  In  some  dictionaries  fermentation  is  referred  to  as  any 
decomposition  of  organic  matter  by  microorganisms,  and  the  products 
may  include  all  products  of  bacterial  decomposition.  In  the  more 
strict  or  more  limited  sense,  however,  fermcjitat ion  applies  to  the  ])eculiar 
action  of  yeasts  or  bacteria  which  involves  the  destruction  of  sugar,  or 
sugar-like  substances,  i.  e.,  the  carbohydrates.    Real  putrefaction  means 


PUTREFACTION  AND   DIGESTION  145 

decomposition  of  alhuininons  substances,  i.  e.,  ])r()teiiis.  In  a  purely 
scientific  sense  putrefaction  is  that  kind  of  albumin  decomposition 
which  is  so  well  illustrated  by  cadaveric  putrefaction,  the  putre- 
faction that  is  accompanied  by  the  evolution  of  products  that  have 
a  very  offensive  odor,  as  the  natural  decay  of  any  dead  animal  body. 
Such  putrefaction  can  take  place  in  the  absence  of  oxygen.  This  kind 
of  putrefaction  occurs  in  deep  cavities  in  teeth  in  which  lodged  food 
has  for  some  time  been  undergoing  decay  and  free  atmospheric 
oxygen  has  been  excluded. 

Certain  kinds  of  bacteria  are  both  fermentative  and  putrefactive, 
acting  on  both  sugars  and  proteins.  Some  are  fermentative  only,  in 
the  pure  sense  of  the  word ;  others  wall  attack  proteins  only.  Certain 
organisms  are  able  to  decompose  various  kinds  of  sugars;  others  will 
attack  only  the  simpler  ones,  like  grape  sugar,  and  have  no  power  at 
all  to  decompose  other  carbohydrates. 

Examples  of  fermentative  organisms  may  be  found  among  the  com- 
mon bacteria  of  the  mouth,  and  the  ordinary  acid-producing  bacteria 
in  milk.  Among  the  fermentation  products  are  acids  of  various  kinds, 
especially  lactic  and  butyric  acids.  Other  decomposition  ])roducts  are 
carbon  dioxid  (CO2)  and,  in  some  instances,  alcohol.  The  different 
acids  can  be  identified.  Any  organism  which  is  able  to  produce  both 
fermentation  and  putrefaction  prefers,  as  a  rule,  the  sugar,  and  there  is 
pronounced  acid  production  long  before  any  sign  of  bacterial  putre- 
faction. Hence,  protein  decomposition  is  for  the  time  prevented,  and 
will  take  place  only  after  the  sugars  are  used  up.  The  acids  may  in- 
crease in  sufficient  amount  to  hold  back  the  growth  of  the  bactera 
that  produce  them,  just  as  in  the  case  of  yeast  fermentation  the 
alcohol  after  a  while  prevents  further  development  of  the  yeast  cells 
that  produce  it.  Alcohol  and  carbon  dioxid  are  the  characteristic 
products  of  yeast  fermentation,  though  they  may  be  included  among 
the  decomposition  products  of  other  bacteria. 

In  order  to  study  putrefaction  and  putrefactive  products  we 
must  choose  an  organism  that  has  the  ability  to  decompose  a 
protein  like  those  of  ordinary  blood  serum  or  egg  white.  When 
these  albumins  are  heated  sufficiently  they  begin  to  thicken  or  coagu- 
late. They  do  not  stand  heating  without  a  change  in  their  physical 
character.  When  these  coagulated  proteins  are  subjected  to  putre- 
factive decomposition  the  first  visible  change  is  usually  the  solution 
or  liquefaction  of  the  insoluble  matter.  Soluble  proteins  are  first 
produced.  These  are  broken  up  into  smaller  and  smaller  products 
until  the  final  stage  of  putrefaction  is  reached. 

PUTREFACTION  AND  DIGESTION. 

An  analogy  may  be  drawn  between  general  putrefaction  and  ordinary 
digestion   in   the   human   body.      The   soluble   proteins    (immediate 
products  of  decomposition)  will  stand  heating.    They  may  be  heated 
10 


H6  BACTERIOLOGY  AND  STERILIZATION 

in  aqueous  solution,  and  they  will  not  harden  or  coagulate.  Peptone, 
for  instance,  is  one  of  these.  Peptone  and  albumose  are  the  im- 
mediate products  of  enzyme  action  upon  protein.  Exactly  similar 
conditions  are  found  in  bacterial  decomposition  of  proteins.  Not 
only  are  there  these  early  products  of  ordinar^^  pancreatic  digestion, 
but  also  various  other  products  that  are  common  to  both  processes. 
Up  to  a  certain  point  bacterial  decomposition  follows  the  very  same 
phases  or  stages  as  those  seen  in  pancreatic  digestion.  The  next 
products  after  soluble  proteins  are,  among  others,  tyrosin  and  leucin, 
which  are  iriiportant  nitrogenous  substances.  They  are  not  albuminous 
in  character  any  more.    They  are  comparatively  simple  products. 

There  is  another  important  product  that  is  common  to  bacterial 
and  tryptic  digestion,  namely,  tryptophan.  In  real  putrefaction  there 
are  subsequent  phases,  however,  which  distinguish  bacterial  decom- 
position from  ordinary  enzyme  action. 

^Yhen  putrefactive  processes  are  allowed  to  continue  indefinitely, 
or  until  the  final  stages  are  reached,  the  characteristic  putrefaction 
products  known  as  indol,  skatol,  phenol,  and  frequently  mercaptan 
are  formed;  also  hydrogen  sulphide,  and  finally  the  simple  products, 
ammonia,  hydrogen  and  carbon  dioxid. 

BACTERIAL  POISONS. 

A  great  deal  has  been  said  in  past  years  about  bacterial 
poisons  kno\Mi  as  ptomaines.  Brieger  succeeded,  apparently,  in 
isolating  many  of  the  so-called  ptomaines.  He  did  more  along  this 
line  of  investigation  than  anybody  else.  He  had  his  own  peculiar 
methods  of  isolating  from  various  bacterial  mixtures  chemical  sub- 
stances that  were  very  toxic  to  animals;  but  many  of  these  toxins  were 
in  all  probability  the  result  of  the  vigorous  treatment  to  which  the 
bacterial  mixtures  were  subjected  in  the  process  of  purification,  instead 
of  being  original  bacterial  products. 

The  former  idea  of  ptomaines  has  been  greatly  modified  in  recent 
years,  Vjecause  much  that  had  been  said  about  ptomaines  could  not 
be  substantiated.  It  was  said  that  cheese  at  certain  stages  contained 
ptomaines  or  bacterial  poisons;  that  milk  if  it  were  kept  in  the  ice-box 
too  l(jng  might  be  extremely  dangerous  because  it  contained  bacterial 
prcjducts  known  as  ptomaines;  that  canned  foods  were  frequently 
dangerous,  for  the  same  reason.  This  may  be  true,  but  the  action  of 
ptomaines  as  poisons  has  in  the  past  been  greatly  overestimated. 
It  is  now  thought  that  bacteria  may  produce  products  in  the  process 
of  decay  Avhich  are  more  or  less  injurious,  l)ut  they  are  harmful  in  the 
sense  that  any  foreign  substance  is  harmful  when  it  gets  into  the 
system.  If  foreign  animal  or  vegetable  matter  is  introduced  into 
the  circulation  of  an  animal,  serious  reactions  may  occur,  even  though 
the  tissues  so  introfluced  are  iiorniiil  tissues,  like  blood,  etc.  Foreign 
substances  in  themselves  are  harmful,  when  introduced  into  the  blood 


IMMUNITY,    VACCINES  AND  ANTITOXINS  147 

circulation  of  auimuls.  In  this  sense  many  bacterial  products  and 
bacteria  themselves  are  injurious,  but  this  due^  not  signify  that  they 
are  necessarily  toxins  or  producers  of  toxins. 

There  is  much  misconception  as  to  the  significance  of  toxins.  Real 
toxins  are  known  in  comiection  with  si)ecific  kinds  of  bacteria  which 
ha\e,  in  addition  to  their  property  of  producing  various  decomposition 
products,  the  peculiar  ability  to  produce  special  substances  known  as 
poisons  or  toxins. 

It  is  assumed,  for  example,  that  the  ordinary  pneumococcus,  an 
organism  present  in  the  mouths  and  lungs  of  pneumonia  patients, 
produces  a  specific  pneumonic  toxin.  Bnt  in  ordinary  dental  decay 
there  is  no  indication  that  the  bacteria  involved  are  toxin  producers, 
although  it  is  quite  probable  that  the  continued  absorption  of  their 
})roducts  by  the  body  is  harmful. 

The  various  disease-producing  organisms  are  characterized  by  the 
fact  that  they  produce  their  own  peculiar  toxin  or  poison.  In  lockjaw, 
for  instance,  a  poison  is  produced  which  is  very  closely  related  to  certain 
powerfid  vegetable  poisons  known  as  ricin  and  abrin.  Chemically 
they  are  not  the  same,  but  in  their  intensity  of  action  they  have  much 
in  common. 

IMMUNITY,  VACCINES  AND  ANTITOXINS. 

It  has  been  previously  stated  that  general  infection  depends  upon 
two  things:  (1)  the  virulence  of  the  infecting  agent,  and  (2)  the 
relative  susceptibility  or  immunity  of  the   subject. 

There  are  two  kinds  of  immunity:  (a)  natural  and  (6)  acquired. 
Xatural  immunity  may  be  inherent  owing  to  some  peculiar  process  in 
racial  development  that  cannot  be  explained.  For  instance,  man  is 
immune  to  fowl  cholera,  while  the  barnyard  fowl  is  very  susceptible 
to  it.  The  human  race  is  susceptible  to  the  typhoid  bacillus.  The 
fowl,  on  the  other  hand,  does  not  contract  typhoid  fever;  in  fact,  none 
of  the  lower  animals  do.  All  species  are  apparently  susceptible  to 
tuberculosis. 

Susceptibility  may  vary  in  a  family.  One  member  may  be  extremely 
prone  to  tuberculosis  or  typhoid  fever;  another  may  be  comparatively 
immune.  It  is  impossible  to  say  why.  Susceptibility  also  varies  from 
day  to  day,  and,  in  fact,  from  hour  to  hour.  The  immunity  of  the 
individual  is  never  constant. 

Immunity  varies  among  individuals  of  the  same  species,  and  in  the 
same  individuals.  There  are  persons  who  carry  the  typhoid  bacillus 
in  their  intestines  day  after  day  and  have  never  shown  signs  of  typhoid 
fever;  diphtheria-carriers   are  often  immune  to  diphtheria. 

Acquired  immunity  is  that  which  results  from  specific  infection  or 
poisoning  of  one  kind  or  another,  or  is  the  result  of  treatment  with 
infmunity-conferring  agents  like  antitoxic  sera.  Actively  acquired 
innnunity  difl'ers  from  passive  immunity  in  that  it  is  the  result  of  an 
actual  disease  process. 


148  BACTERIOLOGY  AND  STERILIZATION 

A  person  who  has  gone  through  smallpox  has  attained  actively 
acquired  immunity.  Another  individual  may  be  more  or  less  immune 
to  smallpox,  by  virtue  of  a  relatively  high  degree  of  natural  immunity. 

Acquired  immunity  may  be  naturally  or  artificially  produced.  In 
the  laboratory  it  is  possible  to  bring  about  artificial  immunity  by 
inoculating  a  guinea-pig  with  a  microorganism  that  is  pathogenic  for 
this  animal.  For  example,  a  broth  culture  of  the  diphtheria  bacillus, 
or  its  poisons,  may  be  injected  in  small  amount  under  the  skin  of  a 
guinea-pig.  If  the  dose  is  very  toxic,  or  if  the  organism  is  virulent 
enough,  the  guinea-pig  will  die  in  a  very  short  time.  If  the  dose  is  not 
fatal,  the  guinea-pig  may  show  signs  of  disturbances,  but  it  will  soon 
recover.  A  second  and  larger  dose  is  then  injected  under  the  skin  and 
the  guinea-pig  in  due  time  recovers  from  the  effect  of  this  also.  If  the 
injection  be  repeated  several  times,  such  a  high  degree  of  immunity 
will  be  reached  that  relatively  large  amounts  of  the  bacillus  or  toxin 
may  be  given  without  any  evil  effect.  Artificially  acquired  immunity 
has  thus  been  brought  about.  The  process  is  analogous  to  that  which 
takes  place  in  a  diphtheria-infected  child.  The  symptoms  are  different, 
but  the  process  is  essentially  the  same.  The  child  has  naturally 
acquired  the  disease,  while  the  guinea-pig  artificially  acquired  it. 

Vaccines. — Not  only  living,  but  dead  bacteria  may  be  employed  to 
produce  immunity.  Such  a  preparation  is  known  as  a  vaccine,  which  is, 
as  a  rule,  nothing  more  than  a  mass  of  dead  bacteria  and  their  products, 
suspended  in  a  suitable  medium.  Such  a  vaccine  when  properly 
applied  will  produce  partial  or  complete  immunity.  The  method  of 
application  is  often  by  hypodermic  injection. 

In  immunization  against  typhoid,  plague,  chronic  abscesses,  especi- 
ally internal  abscesses,  etc.,  cultures  of  the  specific  bacteria  in  question 
are  used.  The  most  common  organism  in  abscess  pus  is  known  as  the 
staphylococcus.  The  staphyloccK'cus  vaccine  is  usually  prepared  from 
the  particular  organism  that  is  causing  the  abscess  in  question,  if  it 
is  possible  to  isolate  it.  Such  a  vaccine  is  called  autogenous,  i.  e.,  it  is  a 
vaccine  prepared  from  the  very  organism  that  is  causing  the  trouble. 
This  bacterium  is  isolated  by  obtaining  a  specimen  from  the  seat  of 
injury  and  cultivating  it  in  an  artificial  medium.  Before  the  vaccine 
is  used  the  bacteria  are  killed  by  heat.  In  the  preparation  of  a  staphy- 
lococcus or  streptococcus  vaccine  heating  at  58°  to  60°  C.  for  about 
one  hour  is  sufficient  to  kill  all  of  the  micrococci.  The  vaccine  is 
therefore  a  suspension  of  dead  bacteria.  Some  vaccines  are  now  being 
advocated  in  which  the  microorganisms  have  not  been  killed,  l)ut  the 
use  of  such  vaccines  is  accompanied  by  more  or  less  danger  from 
infection.  Vaccines  which  have  been  heated  and  still  retain  their 
power  to  produce  at  least  partial  immunity,  are  of  much  value,  and 
comparatively  safe. 

Pathogenic  staphylococci  and  streptococci  admirably  serve  for  the 
preparation  of  the  autogenous  vaccine.  A  suspension  of  these  organ- 
isms which  have  been  isolated  from  the  patient  in  question,  or  from  the 


IMMUNiTY,    VACCINES  AND  ANTITOXINS  149 

abscess  itself,  and  grown  in  pure  culture,  is  heated  at  58°  to  (30°  C, 
for  one  to  one  and  a  half  hours,  and  then  standardized.  This  consti- 
tutes the  final  vaccine.  In  standardizing  vaccines,  the  bacteria  are 
counted  under  the  microscope,  so  that  the  strength  of  the  suspension 
may  be  known,  and  the  necessary  dilutions  made. 

What  do  vaccines  do  when  intelligently  used?  They  are  not  able 
to  effect  serious  injury,  but  may  produce  the  disease  in  question,  in 
very  light  form.  The  symptoms  are  so  mild,  as  a  rule,  that  they  are 
borne  wdth  little  or  no  discomfort.  A  person  receiving  an  autogenous 
vaccine,  or  any  other  kind  of  vaccine,  is  subjected  to  a  method  of 
active  immunization. 

Vaccine  is  now  being  used  for  the  prevention  of  typhoid  f^ver. 
Many  persons  going  to  the  tropics  resort  to  antityphoid  inoculation. 
The  vaccine  is  injected  with  a  small  hypodermic  needle  under  the 
skin  of  the  arm.  Two  or  three  injections  are  made  at  intervals  of  a 
few  days.  One  half  to  one  billion  of  bacteria  are  introduced  during 
each  treatment.  After  the  first  injection  there  is  often  a  little  rash 
and  some  irritation.  Sometimes  there  is  a  rise  in  temperature  and 
slight  bodily  ailment.  These  effects  pass  off  very  soon,  however,  and 
the  subject  becomes  normal.  Real  typhoid  fever  cannot  be  produced 
without  the  living  typhoid  bacillus,  so  there  is  no  danger  of  producing 
the  disease  by  injecting  this  vaccine.  Persons  who  receive  two  or 
three  vaccine  inoculations  against  typhoid  are  likely  to  be  relatively 
immune  to  an  attack  of  typhoid  in  the  course  of  the  next  year  or 
two  at  least.  Vaccination,  therefore,  is  a  process  of  partial,  active 
immunization. 

Antitoxins.^In  the  manvjactvre  of  senim,  or,  in  other  words,  anti- 
toxin production,  several  steps  are  necessary,  which  are  altogether  dif- 
ferent from  those  followed  in  vaccine  production.  A  child  who  receives 
diphtheria  antitoxin  is  made  artificially  immune  by  this  substance; 
but  he  is  not  put  through  an  active  course  of  diphtheria  to  acquire  this 
immunity.  There  may  be  a  little  rash  and  a  few  other  minor  disturb- 
ances wdien  the  antitoxin  is  injected,  but  none  of  the  real  symptoms 
of  diphtheria  occur.  When  antitoxin  is  used  to  prevent  or  cure,  the 
child  receives  into  his  system  an  agent  wdiich  confers  passive  immunity. 
This  active  agent  is  present  in  the  blood  serum  of  a  horse  that  has 
been  actively  immunized  against  diphtheria.  Immunity  is  then  pas- 
sively conferred  upon  the  child  by  the  horse,  the  blood  of  the  horse 
containing  the  diphtheria  antitoxin.  The  horse  does  not  acquire  what 
is  called  diphtheria,  but  has,  nevertheless,  been  put  through  a  process 
of  immunization,  by  actual  poisoning,  not  with  the  diphtheria  bacillus 
itself,  but  with  its  poison  or  toxin. 

Technic  of  Making  Antitoxin. — A  small  dose  of  diphtheria  toxin 
is  injected  under  the  skin  of  the  horse.  After  the  reaction  is  over  the 
horse  receives  a  larger  dose  of  the  toxin.  This  dose  is  increased  and 
repeated  until  the  horse  ceases  to  be  visibly  disturbed.  At  this  stage 
the  blood  is  known,  by  specific  tests,  to  contain  an  abundance  of  the 


150  BACTERIOLOGY  AND  STERILIZATION 

antitoxin.  The  blood  is  tested  by  drawing  it  from  a  vein  and  de- 
termining its  power  to  prevent  death  in  an  animal  which  is  inoculated 
with  a  fatal  dose  of  diphtheria  toxin.  A  single  horse  may  furnish 
sufficient  antitoxin  to  protect  hundreds  of  persons  against  diphtheria. 
I'accines  are  more  beneficial  as  preventive  than  as  curative  agents. 
Only  in  comparatively  few  cases  does  marked  improvement  occur 
when  vaccines  or  antitoxins  are  used  after  disease  has  once  set  in. 
Typhoid  vaccine  is  of  much  value  in  preventing  typhoid  fever,  but 
not  of  much  importance  as  a  cure, 

IMMUNITY. 

Theories  of  Immunity. — The  theories  of  immunity  have  always 
been  a  subject  of  great  interest  and  may  be  discussed  with  profit. 

A  person  may  become  actively  immune  by  going  through  an 
attack  of  smallpox.  The  individual,  after  recovery,  is  immune  at 
least  for  many  years.  One  may  be  vaccinated  against  smallpox  and 
go  through  a  mild  attack  of  disease  somewhat  akin  to  it,  and  acquire 
immunity  which  lasts  for  at  least  several  years.  Now,  why  is  immunity 
acquired  after  having  gone  through  the  natural  disease,  and  why  is  an 
individual  immune  to  smallpox  for  several  years  at  least,  after  having 
been  vaccinated  successfully  against  smallpox? 

Why  does  the  child  who  recovers  from  a  severe  attack  of  diphtheria 
remain  immune  to  diphtheria  for  some  time  to  come? 

The  answers  to  these  questions  are  difficult  ones,  and  are  merely 
theories  and  hypotheses.  However,  in  these  cases  theories  are  of  value 
because  they  are  working  hypotheses.  In  the  laboratory  an  endless 
amount  of  experimental  work  can  be  done  with  the  aid  of  some 
of  these  important  theories  of  immunity.  Furthermore,  they  are 
important  factors  in  modern  preventive  and  curative  medicine. 

One  of  the  old  theories  that  has  merely  an  historical  interest  is  the 
theory  of  retention,  which  was  advanced  many  years  ago.  According 
to  this  theory  certain  chemical  substances  are  retained  in  the  body 
during  the  progress  of  the  disease,  just  as  in  culture  tubes  all  sorts  of 
bacterial  products  accumulate.  These  retained  substances  become  so 
abundant  that  the  bacteria  that  have  produced  them  are  unable  to 
grow  any  longer,  and  they  succumb  to  their  own  poisons. 

Another  old  theory  is  the  theory  of  exhavstion.  This  is  equally 
unworthy  of  serious  consideration,  but  at  the  same  time  it  is  interesting 
historically. 

According  to  the  theory  of  exhaustion  the  bacteria,  after  they  have 
multiplied  in  the  body  of  the  host  for  a  certain  length  of  time,  have 
used  up  the  most  desira})le  and  nutritious  material  or  pabulum,  and 
are  unable  to  thrive  any  longer. 

Both  of  the  above  theories  have  been  set  aside. 

Metchnikoff  originated  a  most  ingenious  theory,  which,  up  to 
ten  or  fifteen  years  ago,  was  looked  upon  with  a  great  deal  of  favor. 


IMMUNITY  151 

This  is  to  the  effect  tliat  the  animal  body  is  normally  endowed  with 
certain  elements  which  have,  as  one  of  their  chief  functions,  the  destruc- 
tion of  foreign  substances  which  invade  the  body.  These  elements 
are  certain  white  blood  cells  which  are  called  phagocytes;  hence  the 
term  phagocytosis.     This  is  the  theory  of  phagocytosis: 

In  the  blood  there  are  various  chemical  substances  in  solution,  as  for 
example,  albumin.  There  are  also  insoluble  elements  or_suspended 
cells  that  are  called  blood  corpuscles.  Of  these  the  most  conspicuous 
are  the  red  and  white  cells.  The  red  cells  contain  the  coloring  matter, 
and  play  an  important  part  in  the  oxygenation  of  the  tissues  of  the 
body. 

These  red  cells  according  to  the  Metchnikoft'  theory  have  nothing 
to  do  with  immunity,  but  the  white  cells,  or  leukocytes  play  an  im- 
portant part. 

A  concrete  example  of  phagocytosis  may  be  given.  A  person  who 
has  gone  through  an  attack  of  pneumonia,  has  become  immune. 
According  to  Metchnikoff,  when  new  pneumococci  invade  this  person 
they  are  destroyed  very  soon  by  the  white  blood  cells  known  as 
phagocytes.  The  phagocytes  which  come  into  contact  with  these 
organisms  take  them  within  themselves  and  destroy  them  by  a  process 
of  dissolution  and  digestion.  In  a  susceptible  individual  the  phagocytes 
are  so  few,  or  they  are  so  weak  that  the  invading  bacteria  gain  the 
upper  hand  and  disease  develops. 

These  phagocytes  may  be  seen  at  work  under  the  microscope. 
If  a  large  bullfrog  is  given  a  mild  attack  of  anthrax  by  injecting  a 
pure  culture  of  this  bacillus  into  one  of  the  lymph  spaces  on  the  back 
or  abdomen  and  then  the  lymph  of  the  frog  is  examined,  a  most 
interesting  picture  will  be  observed.  The  anthrax  bacilli  will  be  seen 
lying  within  the  phagocytes,  some  apparently  unchanged  and  normal, 
with  definite  outlines,  as  if  they  were  still  able  to  multiply  and  perform 
their  various  functions,  while  others  are  in  the  process  of  disintegration. 

Metchnikoff's  theory  for  a  long  time  received  much  support,  but 
finally  had  to  be  materially  modified. 

Certain  of  the  blood  leukocytes,  the  phagocytes,  according  to 
Metchnikoff's  idea,  are  able  to  ingest  and  destroy  invading  foreign 
organisms,  and,  among  them  bacteria,  but  they  are  unable  to  do 
this  unaided;  they  require  assistance  of  certain  chemical  immune 
substances  known  as  opsonins  which  are  present  in  immune  blood  in 
varying  amounts.  The  theory  of  phagocytosis  is  still  maintained, 
but  in  modified  form. 

The  most  interesting  of  all  theories,  and  probably  the  most  important 
in  many  respects  is  Ehrlich's  side-chain  theory. 

As  an  example  it  will  be  assumed  that  a  child  is  recovering  from 
diphtheria.  By  experiment  it  is  known  that  while  the  child  is  throw- 
ing off  the  disease  or  is  recuperating,  it  is  fortifying  itself  against 
future  attacks,  and  also  against  further  injury  from  the  present 
attack. 


152  BACTERIOLOGY  AND  STERILIZATION 

It  has  been  demonstrated  again  and  again  that  if  a  small  amount 
of  blood  be  taken  from  a  person  recovering  from  diphtheria,  or  from 
an  immunized  animal,  and  be  brought  in  contact  with  an  ordinarily 
fatal  dose  of  diphtheria  toxin,  that  the  diphtheria  toxin  is  neutralized, 
and  is  harmless  when  injected'  into  a  susceptible  animal. 

In  other  words,  the  serum  of  the  blood  of  an  animal  which  has  been 
immunized  against  diphtheria  has  the  property  of  protecting  a  normal 
guinea-pig  against  a  fatal  dose  of  the  toxin.  If  this  is  so,  then  it  must 
be  assumed  that  when  a  person  throws  off  the  disease,  or  recovers  com- 
pletely, he  has  produced  something  in  his  own  body  which  is  injurious 
or  antagonistic  to  the  bacteria  and  toxins  that  in  the  first  place  pro- 
duced the  disease.  Hence  the  terms  antitoxins  and  antibodies.  An 
antibody,  therefore,  is  nothing  more  than  something  which  has  been 
produced  as  the  result  of  poisoning  or  infection,  a  substance  or  sub- 
stances within  the  body,  which  counteract  and  neutralize  the  poisons 
or  the  bacteria  in  question. 

Ehrlich's  Side-chain  Theory  of  Immunity. —  Toxins  are  peculiar 
chemical  substances  that  may  be  characterized  as  possessing  two 
distinct  functional  parts,  one  that  acts  as  the  poison,  and  the  other 
that  serves  as  a  link  to  connect  the  toxin  with  tissues  that  are 
attacked.  The  former  will  be  called  the  poisoning  group,  and  the 
latter,  the  combining  group.  As  long  as  toxins  are  uncombined  with 
the  tissues  they  are  harmless,  but  just  as  soon  as  the  combining  group 
comes  in  contact  with  any  part  of  the  tissue  the  poisonous  group  exerts 
its  poisonous  action.  Without  this  combination  the  toxin  is  absolutely 
harmless. 

In  the  natural  course  of  events  the  toxins  actually  do  find  occasion 
to  combine  with  some  of  the  tissues.  The  parts  of  the  attacked  tissues 
to  which  the  toxins  become  attached  are  called  by  Ehrlich  receptors 
or  side  chains.  ]More  and  more  toxins  combine  with  side  chains 
as  this  process  goes  on,  until  there  comes  a  time  when  the  subject 
responds  in  one  of  two  ways,  i.  e.,  he  either  succumbs  to  the  disease 
or  begins  to  make  his  recovery.  If  he  recovers,  the  following  ex- 
planation is  given  in  the  Ehrlich  theory:  When  the  toxins  combine 
with  the  side  chains,  the  tissues  which  are  affected  cast  off  the  poisoned 
side  chains  and  immediately  produce  new  ones  to  take  their  place. 
The  injured  side  chains  are  thrown  off  in  order  to  protect  the  main 
tissues  or  cells  themselves.  They  have  simply  been  sacrificed  and 
float  about  in  combination  with  the  toxins  whose  aetion  they  neutralize. 
Finally,  they  become  dissolved  or  digested  by  the  body  fluids.  But  a 
most  interesting  fact  is  that  thes(;  tissues  have  the  peculiar  i>r()perty 
of  some  of  the  lower  animals,  like  the  salamander,  of  restoring  lost 
members.  These  tissues,  when  they  lose  a  side  chain,  immediately 
replace  it.  If  they  lose  two  side  chains,  they  replace  them.  If  they 
lose  a  thousand,  they  will  replace  a  thousand,  and  soon  they  acquire 
the  habit  of  reproducing  not  only  the  lost  rcc('i)tors,  })ut  more  than  the 
number  sacrificed,  and  so  where  one  side  chain  has  been  lost  there  will 


STERILIZATION  AND  DISINFECTION  153 

be  dozens  to  take  its  ])lace.  The  cells  have  prothiced  these  side  chains 
in  such  large  numbers  that  the  toxin  is  insufficient  in  amount  to  com- 
bine with  all  of  the  newly  formed  receptors.  Furthermore,  the  side 
chains  are  produced  in  such  large  numbers  that  the  tissue  cells  cannot 
hold  on  to  them  any  longer.  The  body  fluids  become  filled  with  these 
free  receptors  which  are  now  known  as  the  immune  bodies  or  cmti- 
toxins. 

The  antitoxins  are  the  side  chains  that  have  been  produced  in  such 
large  numbers  that  the  very  tissues  from  which  they  were  generated 
can  no  longer  retain  them,  and  they  are  shot  oft*  into  the  circulation 
and  remain  there  as  safeguards  against  any  other  toxins  that  may 
invade  the  tissue.  If  toxins  present  themselves,  they  will  combine 
with  these  free  antitoxins  and  thus  no  injury  will  be  wrought  on  the 
tissues.  The  antitoxins  are  in  the  blood  floating  about  freely,  and 
combine  with  the  individual  toxins,  neutralizing  them,  and  preventing 
the  toxins  from  getting  at  the  living  sensitive  tissues  themselves. 

This  is  one  of  the  most  ingenious  and  at  the  same  time  one  of  the 
most  satisfactory  theories  of  immunity. 

STERILIZATION  AND  DISINFECTION. 

There  are  three  important  phases  of  this  subject  that  have  received 
a  great  deal  of  attention:  (1)  asepsis;  (2)  antisepsis;  and  (3)  disin- 
fection.   The  actual  distinctions  are  important. 

In  asepsis  there  is  what  the  term  implies,  absence  of  infection,  or 
absence  of  sepsis;  that  is,  in  asepsis  living  bacteria  are  excluded, 
and  where  microorganisms  do  not  exist  there  can  be  no  such  thing  as 
antisepsis  or  disinfection.  The  idea  of  asepsis  is  coming  to  the  front 
more  and  more  in  surgery,  and,  to  a  large  degree,  actually  supplanting 
disinfectants  and  antiseptics. 

The  second  phase,  that  of  antisepsis,  has  its  own  significance. 
Various  food  substances  are  preserved  by  means  of  chemicals.  The 
salting  or  curing  of  pork  is  an  instance.  If  a  thorough  bacteriological 
examination  of  cured  pork  were  made,  it  would  not  be  found  sterile 
but  would,  in  all  probability,  be  found  to  contain  any  number  of 
bacteria.  But  there  is  an  antiseptic  condition,  and  the  bacteria  that 
are  present  are  unable  to  multiply  appreciably  under  such  conditions. 
An  antiseptic  is  an  agent  which  prevents  growth  and  multiplication  of 
bacteria  but  does  not  destroy  them. 

The  third  phase,  disinfection,  deals  with  agents  that  destroy  or  remove 
bacteria,  and  therefore  is  entirely  different  from  either  one  of  the 
other  two  phases.  Asepsis  means  no  bacteria.  Antisepsis  means  the 
holding  in  check  of  bacteria  that  are  present.  Disinfection  means 
the  destruction  or  complete  removal  of  all  bacteria. 

On  entering  a  modern  surgical  operating  room  one  is  impressed  with 
its  appearance.  The  most  up-to-date  surgical  ward  now  depends 
more  on  asepsis  in  ordinary  surgical  operations  than  on  the  other 


154  BACTERIOLOGY  AND  STERILIZATION 

two  phases  of  the  subject.  The  instruments  must  be  steriUzed. 
The  hands  of  the  surgeon  and  his  assistants  are  thoroughly  cleaned 
and  disinfected.  In  some  of  the  best  hospitals  they  do  not  even 
depend  on  washing  and  sterilization  of  the  hands,  but  use  gloves 
that  have  been  sterilized  and  kept  in  an  antiseptic  solution.  The 
air  should  be  perfectly  still.  There  are  operating  rooms  where  per- 
sons are  prevented  from  coming  into  the  room  or  anywhere  near 
the  patient  operated  upon,  until  they  put  on  long,  sterilized  coats. 
Furthermore,  those  who  perform  surgical  operations  frequently  have  a 
mask  over  their  mouth,  so. as  to  prevent  infection  of  the  patient  by 
mouth  spray.  No  mouth  is  ever  found  to  be  sterile,  and  it  is  doubtful 
if  it  ever  will  be  possible  to  sterilize  the  mouth,  so  there  is  no  such 
thing  as  asepsis  in  dentistry  in  the  pure  sense  of  the  word.  But 
asepsis  is  an  important  factor  insofar  as  the  hands  and  the  instruments 
are  concerned. 

It  may  be  said  that  disinfection  involves  the  absolute  destruction 
of  all  forms  of  life.  The  term  is  often  misused,  as  for  example,  in 
connection  with  the  pasteurization  of  milk.  Sterilization  of  milk 
means  the  destruction  of  all  microbic  life,  including  spores.  Steriliza- 
tion of  milk,  or  sterilization  of  water,  is  real  sterilization  only  when 
all  organic  life  is  destroyed. 

There  are  different  degrees  of  purification  by  heat  or  chemicals. 
Pasteurizatio?i  of  milk  is  an  important  example  of  ijicoinyilete  steriliza- 
tion. It  is  neither  antisepsis  nor  disinfection  nor  sterilization.  It  is 
the  destruction  of  the  comparatively  non-resistant  types  of  bacteria 
in  the  milk.  Spores  and  a  small  number  of  resistant  vegetative  forms 
are  not  killed.  In  pasteurization  the  heat  used  is  far  below  the  real 
temperature  for  sterilization.  In  the  ordinary  pasteurizer  the  milk 
is  heated  at  a  temperature  of  140°  to  145°  F.,  for  a  period  of  twenty  to 
thirty  minutes.  Milk  that  is  pasteurized  at  such  a  temperature  will 
keep  much  longer,  and  is  less  apt  to  cause  disease  than  the  unpasteur- 
ized. If  disease-producing  bacteria,  like  the  typhoid  and  the  tubercle 
bacillus,  were  present,  they  have  been  destroyed  in  the  process,  and 
the  milk  has  been  made  safe.  But  that  does  not  mean  that  this  milk, 
when  it  is  put  in  the  ice-box  or  allowed  to  stand  on  the  kitchen  table, 
is  not  undergoing  an}'  further  chemical  or  bacterial  change.  Pasteuri- 
zation simply  holds  in  check.  It  corresponds  to  antisepsis,  but  is  not 
antisepsis,  because  the  pasteurization  is  temporary.  In  antisepsis  the 
antiseptic  influence  is  permanent. 

Methods  of  Sterilization. — In  disinfection  or  sterilization  various 
agencies  may  be  employed  to  bring  about  the  desired  result.  One  of 
the  most  efficacious,  and  one  of  the  most  practical  and  reliable  means 
of  sterilizing  objects  is  heat.  Heat  is  perhaps  the  most  important  of  all 
sterilizing  agents,  and,  of  course,  in  many  professions  it  is  indispensable 
as  such. 

Sterilization  by  dry  heat  is  a  method  that  is  commonly  used  in  labora- 
tories anfi  hospitals.     Glass  plates  or  Petri  dishes  are  sterilized,  before 


STERILIZATION  AND  DISINFECTION  155 

they  are  used,  by  the  hot-air  method  of  steriHzation.  Test-tubes  are 
often  sterihzed,  before  filling,  in  the  same  way. 

There  are  many  occasions  on  which  the  dry-heat  method  cannot  be 
used  and  another  method  of  sterilization  must  be  resorted  to,  namely, 
moist  heat.  Dry  heat  may  be  applied  only  to  certain  objects  that  will 
stand  it.  It  is  not  safe  to  sterilize  ordinary  fabrics  with  dry  heat,  as 
they  are  apt  to  become  discolored  and  charred. 

Steam  heat  will  often  take  the  place  of  dry  heat,  and  is  an  important 
means  of  sterilization.  The  sterilization  of  towels,  of  dressings,  of 
media  that  are  used  in  the  ordinary  laboratory  work,  and  a  large 
number  of  other  objects  that  cannot  be  subjected  to  dry  heat  are 
advantageously  sterilized  in  this  way. 

A  word  may  be  said  about  the  comparative  efficacy  of  dry  and  moist 
heat.  While  dry  heat  may  char  or  discolor  cotton  and  woolen  fabrics, 
it  is  not  nearly  as  effective  in  its  destructive  action  on  bacteria  as  moist 
heat  at  the  same  temperature.  This  fact  should  always  be  borne  in 
mind.  An  illustration  may  be  given.  Some  bacteria,  like  the  diphtheria 
bacillus,  will  stand  a  temperature  as  high  as  that  of  boiling  water  for 
a  short  time  when  in  a  dry  condition,  whereas  a  moist  temperature 
of  150°  F.  applied  for  the  same  length  of  time  is  fatal.  In  other  words, 
moist  heat  is  effective  at  relatively  low  temperatures,  whereas  dry  heat 
is  often  ineffective  at  even  relatively  high  temperatures. 

Spores  are  unusually  resistant  to  heat  and  other  sterilizing  agents. 
They  will  often  withstand  a  moist  temperature  of  212°  F.  for  an  hour. 
When  dry  heat  is  applied  it  is  necessary  to  raise  the  temperature 
to  at  least  300°  F.  and  maintain  it  for  an  hour. 

Frequently  it  it  not  necessary  to  destroy  all  spores,  but  only  such 
organisms  as  possess  disease-producing  powers.  In  such  instances, 
boiling  for  fifteen  to  twenty  minutes,  with  a  small  amount  of  potash 
or  soda  may  be  sufficient. 

Since  in  the  use  of  surgical  and  dental  instruments  there  is  always 
some  danger  of  lockjaw  infection  (caused  by  the  lockjaw  bacillus  or  its 
spore),  thorough  disinfection  should  always  be  made. 

Some  things  are  sterilized  under  pressure.  The  ordinary  barber-shop 
sterilizer,  a  big  globe-shaped  apparatus,  is  a  valuable  instrument  for 
sterilizing  towels,  brushes,  etc.  The  objects  to  be  sterilized  are  put  in, 
the  door  is  placed  in  position,  and  steam  is  generated  by  means  of  a 
gas  lamp,  or  is  introduced  tlu"ough  a  steam  pipe.  The  increase  in  the 
pressure  of  the  steam  becomes  such  that  the  temperature  can  be 
raised  considerably  above  that  of  boiling  water.  Thus,  within  certain 
limits,  any  temperature  may  be  obtained. 

Ordinary  boiling  is  not  sufficient  for  absolute  sterilization.  Wherever 
complete  sterilization  by  moist  heat  is  required,  it  is  imperative  to  use 
a  sterilizer  that  will  heat  under  extra  pressure,  or  to  use  some  chemical 
agent  which  lowers  the  sterilization  temperature.  When  instruments 
are  boiled  in  water  it  is  advisable  to  add  a  small  amount  of  a  solution 


156  BACTERIOLOGY  AND  STERILIZATION 

of  soda  or  potash,  for  the  purpose  of  lowering  the  steriHzation  tempera- 
ture, and  of  pre^'enting  the  instruments  from  rusting. 

Chemicals. — There  is  another  method  of  disinfection,  that  is  by  means 
of  chemicals.  A  great  deal  is  being  done  today  in  the  disinfection  of 
water  supplies,  of  all  sorts  of  surgical  instruments,  clothing,  etc.  Also 
in  aerial  disinfection  of  rooms,  as  with  formaldehyde.  The  disinfection 
of  the  interior  of  rooms,  including  the  hangings,  and  all  sorts  of  articles 
that  may  have  become  infected  by  some  occupant  who  has  had  some 
infectious  disease,  has  been  practised  for  many  years.  In  the  purifica- 
tion of  water  supplies  one  of  the  best  disinfecting  agents  employed  is 
chloride  of  lime. 

A  disinfectant  that  is  being  extensively  used  in  surface  disinfection 
6i  the  body  is  iodine  in  the  form  of  tincture  of  iodine.  This  may  be 
applied  externally  only.  The  choice  of  a  disinfectant  depends  upon  the 
specific  object  to  be  disinfected,  and  in  many  cases,  upon  the  bacteria 
and  spores  that  it  is  intended  to  destroy. 

Corrosive  sublimate  and  carbolic  acid  have  been  used  for  years 
as  general  disinfectants  for  the  hands  and  for  different  portions  of  the 
body  and  body  wastes.  The  bichloride,  usually  in  1  to  1000  dilution, 
and  the  carbolic  acid  in  the  proportion  of  1  to  35  to  1  to  50.  In  fact, 
mercury  bichloride,  or  what  is  known  as  corrosive  sublimate,  has  been 
used  in  past  years  to  a  very  large  extent  in  connection  with  surgical 
operations.  Today  there  is  a  growing  sentiment  against  corrosive 
sublimate,  especially  as  an  internal  disinfectant.  It  contains  mercury, 
and  for  that  reason  it  is  useless  in  the  disinfection  of  metallic  objects 
because  it  attacks  the  metal,  forming  an  alloy  with  it. 

Then  there  are  other  facts  that  make  corrosive  sublimate  and  carbolic 
acid  as  well  more  or  less  worthless.  Both,  and  particularly  the  former, 
will  combine  with  various  chemical  substances,  like  protein,  and  lose 
their  disinfectant  properties. 

Another  disinfectant  that  has  been  used  a  great  deal  is  formalin,  or 
formaldehyde.  In  house  disinfection  it  is  used  as  a  spray,  or  asformalin 
vapor.  Permanganate  of  potash  and  formalin  are  now  used  in  com- 
bination for  the  evolution  of  the  disinfectant  vapor,  the  permanganate 
serving  simply  to  generate  heat  by  its  action  on  the  formalin.  A 
certain  amount  of  moisture  is  always  necessary,  to  obtain  a  high  disin- 
fectant efficiency. 

Sulphur  also  has  been  used  a  great  deal  for  aerial  disinfection  of 
the  interior  of  houses,  but  it  is  useless  unless  there  is  an  abunrlance 
(jf  mf)isture,  which  combines  with  the  suli)hurous  gas,  to  produce 
sulphurous  acid.  While  this  product  is  a  jjowerful  disinfectant,  it 
is  also  destructive  to  furniture,  hangings,  wallpaper,  etc. 

It  is  impossible  as  yet  to  name  a  completely  satisfactory  chemical 
disinfectant,  although  in  recent  years  many  new  ones  have  been  put 
on  the  market.  How  often  does  the  dentist  take  his  instruments,  dip 
them  into  carbolic  acid,  take  them  right  out  again,  and  assume  that 
they  are  sterile  and  ready  for  further  use.     That  is  not  disinfection.    If 


STERILIZATION  AND  DISINFECTION  157 

a  chemical  is  to  be  used  as  a  disinfectant,  it  must  either  be  extremely 
powerful,  or  the  time  that  is  allowed  for  the  disinfectant  to  act  on  the 
subject  to  be  disinfected  must  be  considerable.  It  is  for  that  reason 
too,  largely,  that  boiling  with  a  little  alkali  is  taking  the  place  of 
chemical  disinfection  of  one  sort  or  another,  as  for  example  with  car- 
bolic acid,  carbolized  vaseline,  etc. 

In  determining  the  value  of  a  duinfectant  several  points  are  taken  into 
consideration.  The  time  during  which  the  agent  is  allowed  to  act  is  an 
important  factor  as  well  as  the  temperature.  In  many  cases  the  effi- 
ciency increases  with  increase  in  temperature.  Then  the  conditions 
imder  which  disinfection  takes  place  are  of  much  significance.  A  good 
disinfectant  will  not  lose  its  power  by  contact  with  proteins,  carbonates 
and  other  chemicals.  Finally,  it  must  be  efficient  as  a  disinfectant,  but 
harmless  to  man  or  animal. 

Alcohol  in  a  dilution  of  40  to  80  per  cent,  serves  as  a  valuable  dis- 
infectant, under  certain  conditions.  Recently  ether  has  been  strongly 
advocated  as  a  disinfectant  in  certain  abdominal  operations  and 
treatment.  There  are  many  disinfectants  which  are  powerful  enough 
under  certain  favorable  conditions,  or  when  thoroughly  adapted. 

Soap  is  one  of  the  most  valuable  agents  in  the  elimination  of  bacteria. 
It  is  a  cleanser,  and  surgeons  are  coming  more  and  more  to  the  idea 
that  cleansing  is  of  extreme  importance,  as  well  as  disinfection.  If 
cleansing  can  be  done  at  the  same  time  as  disinfecting,  or  just  before, 
then  disinfection  will  be  doubly  effective.  But  if  the  disinfectant  is 
put  on  over  a  coating  of  dirt  or  grease,  it  is  of  little  value.  Soap,  hot 
water  and  a  nail  brush  will  do  a  great  deal  toward  absolute  disinfection 
of  the  hands.  Soap  alone  has  some  disinfectant  properties  but  its 
chief  value  lies  in  its  cleansing  action. 


CHAPTER  V. 
INFLAMMATIOxX. 

By  LeROY   M.  S.  MINER,  M.D.,  D.M.D. 

IxFLAiMiMATioN  may  well  be  called  the  cornerstone  of  Pathology, 
for  an  accurate  conception  of  the  principles  involved  in  the  phenomena 
of  inflammation  is  necessary  in  order  to  have  a  foundation  upon  which 
to  build  a  knowledge  of  general  pathology. 

Inflammation  in  its  various  forms  is  so  exceedingly  common  that 
without  a  knowledge  of  the  changes  that  take  place  one  cannot  hope 
to  understand  the  manifestations  which  occur  in  diseased  conditions. 

Definition. — Inflammation  may  be  described,  in  a  word,  as  a  response 
or  reaction  to  an  irritation  or  injury.    Its  ijurpose  is  twofold: 

1.  To  counteract  or  neutralize  the  agent  causing  the  injury. 

2.  To  repair  the  injury  produced. 

Thus  it  is  seen  that  inflammation  is  intended  to  be  a  building  up  pro- 
cess; a  beneficial  effort  of  nature  to  repair  damage.  Unfortunately 
it  not  infrequently  happens  that  under  unfavorable  conditions  it 
becomes  rlistinctly  destructive  instead  of  reparative. 

Classification. — The  many  types  of  inflammation  have  been  classi- 
fied in  \arious  w^ays.  The  terms  most  frequently  used,  however,  are 
(1)  acute  and  (2)  chronic. 

It  may  also  be  classified  according  to  the  location.  Catarrhal 
wflammatiov.  affects  the  epithelial  structures,  especially  the  mucous 
membranes;  inflammation  is  said  to  be  Interstitial,  when  the  connec- 
tive or  supporting  tissues  are  involved;  or  Parenchymatous,  when  the 
functionating  cells  of  an  organ  are  attacked. 

Inflammation  has  also  been  described  as  Ulcerative,  when  there  is 
l(xss  of  tissue  by  necrosis  or  gangrene;  Exudative,  when  the  process 
is  characterized  by  unusual  exudates  as  in  pleuritic  effusion;  Swp- 
jmrative,  when  the  inflammation  ends  in  suppuration  or  the  formation 
of  pus. 

While  these  classifications  help  to  describe  the  location  or  the  type 
of  inflammation,  and  while  the  clinical  aspects  may  vary  somewhat, 
it  must  be  firmly  borne  in  mind  that  the  i)henomena  of  the  reactions 
which  take  ])lace  are  essentially  the  same  in  all  forms.  The  location  of 
the  injury  will  determine  to  a  considerable  extent  the  effect,  but  the 
reacti(;n  is  fundamentally  the  same. 

Inasmuch  as  the  cinmlation  of  both  blood  and  lymph  plays  a 
very  important  role  in  the  phenomena  of  inflaniniution,  it  is  neces- 
sary to  have  some  knowledge  of  the  normal  circulation  and  also  some 


THE  CONSTITUENTS  OF  THE  NORMAL  BLOOD  159 

idea  of  tlie  simpler  tissues  wliicli  may  be  affected  before  studying  the 
process  itself. 

The  Normal  Circulation. — The  circulation  of  blood  differs  in  each 
of  the  three  types  of  vessels. 

In  the  arteries,  which  carry  the  fresh  red  blood,  the  flow  is  inter- 
mittent, the  red  blood  corpuscles  flow  in  the  center  of  the  vessel 
(axial  core),  while  between  them  and  the  vessel  wall  is  a  colorless 
zone  called  the  plasma  zone.  The  white  blood  corpuscles  travel  in 
this  zone  and  travel  much  more  slowly  than  the  red  corpuscles. 

In  the  capillaries,  or  the  intermediate  vessels,  the  blood  flow  is 
slow  and  continuous.    There  is  no  plasma  zone. 

The  flow  in  the  mins  is  continuous  and  slower  than  in  the  arteries. 
The  plasma  zone  is  present,  but  less  sharply  defined  than  in  the 
arteries. 

The  Constituents  of  the  Normal  Blood.— The  chief  constituents  of 
the  normal  blood  are  eight  in  number,  as  follows: 

I.  Red  blood  corpuscles,  erythrocytes.      J^^    • 
II.  Blood  platelets.  -^sJ.<r^-^ 

III.  Polymorphonuclear  leukocytes  (leukocytes  with  many  nuclei) .f^ 
1\.  Endothelial  leukocytes. 
V.  Lymphocytes. 
VI.  Eosinophiles. 
VII.  Mast  cells. 

Vm.  Blood  plasma. 

Groups  III  to  VII  are  various  types  of  white  blood  cells. 

The  red  blood  corpuscles  are  bell-  or  cup-shaped  masses  of  cytoplasm 
containing  no  nucleus.  One  cubic  millimeter  of  blood  under  normal 
conditions  contains  4,500,000  to  5,000,000  red  corpuscles  and  at  birth 
about  6,000,000.  These  corpuscles  are  not  permanent  cells,  but  are 
short-lived.  Their  function  is  the  carrying  of  oxygen,  w^hich  forms  a 
loose  combination  with  hemoglobin,  which  is  the  most  important 
constituent  found  in  the  protoplasm  of  these  cells.  The  red 
blood  corpuscles  are  derived  from  the  erythroblasts  of  the  bone- 
marrow. 

The  blood  platelets  are  round  or  oval  disks  about  one-half  the 
size  of  the  red  blood  corpuscles.  One  cubic  millimeter  contains 
250,000  to  500,000  platelets. 

The  ivhite  corpuscles  grouped  together  are  present  in  much  smaller 
numbers  than  the  red  blood  corpuscles,  there  being  only  8000 
per  centimeter  on  the  average.  There  are  about  600  red  to  1  white 
corpuscle. 

The  polymorphonuclear  leukocytes  are  the  most  frequently  found 
white  corpuscles  and  form  70  to  72  per  cent,  of  the  total  number.  They 
are  larger  than  the  red  blood  corpuscles.  Under  the  microscope  the 
nucleus  of  this  cell  attracts  attention.  The  nucleus  is  irregular  and 
has  rounded  lobules.  The  cell  membrane  is  sharply  defined.  These 
cells  are  formed  in  the  bone-marrow  also. 


]  00  IN  FLA  MM  A  TION 

EndoihvViaJ  Ictilcoci/tes  or  mononncJear  leukocytes  are  larger  even 
than  the  ix)lyni()rphonuclear  cells,  being  two  or  three  times  as  large  as 
the  red  blood  corpuscles.  In  number  they  make  up  only  2  to  4  per 
cent,  of  all  the  white  cells.  They  are  derived  from  the  endothelial 
cells  lining  the  bloodvessels. 

The  lymphocytes  are  found  most  frequently  next  to  the  polynuclear 
cells.  They  form  22  to  25  per  cent,  of  all  the  white  corpuscles. 
They  are  about  the  size  of  the  red  corpuscles.  The  appearance  is 
characteristic.  The  cells  are  round  and  they  take  the  stain  well, 
especially  the  periphery.  Lymphocytes  are  produced  in  lymphoid 
tissue  and  especially  in  the  lymph  nodes. 

Eosinophiles  make  up  2  to  4  per  cent,  of  the  total  leukocytes.  The 
nucleus  is  frequently  shaped  like  a  horseshoe,  and  the  cell  itself  may 
be  larger  than  the  polynuclear  leukocytes.  It  derives  its  name  from 
the  intense  staining  with  eosin.    They  are  derived  from  bone-marrow. 

The  viast  cells  make  up  but  five-tenths  of  1  per  cent.  They 
are  also  derived  from  bone-marrow. 

Blood  plasma  is  the  fluid  part  of  the  blood  and  contains  fibrin, 
which  ])lays  an  active  part  in  the  phenomena  of  coagulation.  With 
the  fibrin  removed  the  plasma  is  called  serum. 

In  addition  to  this  brief  study  of  the  blood  and  its  circulation  it 
may  be  well  to  mention  some  of  the  basic  histological  structures  which 
are  concerned  in  the  study  of  the  inflammatory  process.  They  are 
as  follows : 

I.  Connective  tissue  (fibroblasts). 
11.  Endothelial  cells. 

III.  Nerves. 

IV.  Lymph  vessels  and  spaces. 
V.  Bloodvessels. 

Connective  Tissue. — The  function  of  this  tissue,  as  the  name  suggests, 
is  to  bind  or  support  other  tissue.  The  cell  of  which  it  is  formed  is 
called  the  fibroblast.  These  cells,  as  a  rule,  are  flat,  elongated  cells 
with  o\al  nuclei.  The  fibroblast  frequently  plays  an  important  part 
in  inflammatory  processes. 

Endothelial  Cells. — These  cells  line  the  blood  and  lymph  vessels. 
In  form  they  are  flattened  and  have  an  oval  nucleus. 

The  inflanmiatory  process  may  be  divided  into  three  parts: 
I.  The  injurious  agent  or  the  cause. 
II.  The  injury  done  to  the  tissues. 

TIL  '^riie  resulting  reaction  to  the  injurious  agent  and  to  the  injury. 
The  Injurious  Agent  or  Cause. — Some  writers  have  classified  the  causes 
of  inflammation  under  two  headings: 
L  The  jjredisposing  cause. 
2.  The  exciting  cause. 
As  a  ])redis])osiv(i  cause  of  inflammation  age  may  be  mentioned. 
In  growing  cliiidren,  the  nutritional  and  developmental  changes  pre- 
dispo.se  to  inflammation  of  the  mucous  membranes.    The  frequency 


CAUSES  OF  INFLAMMATION  101 

of  stomatitis  in  children  is  an  exam])le.  In  okl  age  the  lowerinj^  of 
the  resistance  pre(lisi)()ses  to  the  inflammations  of  bacterial  orij^nn. 
Bronchitis  is  an  example.  Fatigue  and  worry  are  said  to  be  predis- 
posing causes.  Any  condition  that  lowers  the  natural  resistance  may 
be  regarded  as  a  predisposing  cause. 

The  exciting  cause,  or  the  active  injurious  agents  may  be  divided 
into  tliree  groups: 

I.  Mechanical:  cuts,  blows,  foreign  bodies. 
II.  Physical:    heat,   cold,    sunlight   (sunburn),   electricity,   .f-ray, 

radium. 
III.  Chemical: 

(a)  Inorganic  c()m])ounds:   acids,  alkalies,  j)oisons. 

(b)  Organic:  microorganisms,  bacteria  and  their  toxins. 
This  last  group,  especially  the  bacteria,  form  the  chief   cause   of 

inflammation.  In  fact,  so  common  is  bacterial  invasion  the  cause 
that  it  has  been  incorrectly  assumed  that  inflammation  was  dependent 
upon  bacteria  or  their  products.  As  a  matter  of  fact  the  lesions  pro- 
duced by  the  injurious  agents  other  than  bacteria  are  identical  to 
those  of  bacterial  origin. 

It  is  not  necessary  to  go  into  great  detail  regarding  the  bacteriology 
of  inflammation,  but  some  of  the  more  common  bacteria  may  be  briefly 
described.  The  three  most  common  organisms  are  the  Staphylo- 
coccus pyogenes  aureus.  Streptococcus  pyogenes  and  the  pneumo- 
coccus. 

The  staphylococcus  is  found  on  the  skin,  or  in  the  mouth,  and  is 
very  common.  It  may  possess  little  or  no  virulence,  or  it  may  become 
extremely  pathogenic  when  abnormal  conditions  exist.  It  is  the  most 
frequent  organism  found  in  pus.  It  is  a  small,  round  cell  and  tends 
to  form  in  groups  or  clusters.  When  grown  artificially  it  produces 
a  distinctly  yellowish  color  in  the  medium. 

The  streptococcus  is  a  more  dangerous  organism,  but  it  is  not  so 
common  as  the  staphylococcus.  It  is  not  infrequently  found  in  the 
mouth  and  nose.  It  is  often  found  in  suppurative  conditions  with 
the  staphylococcus.  It  is  a  spherical  organism  which  has  the  char- 
acteristic of  growing  in  chains. 

The  pneumococcus  is  found  frequently  in  inflammatory  conditions. 
It  is  said  to  be  a  normal  inhabitant  of  the  mouth.  ^Morphologically 
these  organisms  appear  like  elongated  cocci  and  tend  to  grow  in  pairs 
or  short  chains.  Under  some  conditions  a  well-defined  capsule  is  seen. 
This  organism  has  been  found  very  frequently  in  the  inflammatory 
conditions  of  the  alveolar  process,  commonly  known  as  pyorrhea 
alveolaris.  The  Bacillus  pyocyaneus,  typhoid  bacillus,  colon  bacillus 
and  tubercle  bacillus  are  other  notable  examples  of  pathogenic 
bacteria  which  produce  their  more  or  less  characteristic  inflam- 
mations. 

The  action  of  an  injurious  agent  may  be  severe  or  slight,  brief  or 
prolonged.  The  effect  varies  accordingly.  Some  agents  produce  a 
11 


162  INFLAMMATION 

lesion  very  quickly,  others  only  after  acting  over  a  long  period  of  time. 
The  action  may  be  local  or  general:  local,  as  in  the  case  of  a  blow; 
general,  as  in  the  case  of  diphtheria  toxin. 

The  Injury. — Befinitioiis. — Injury  is  the  term  applied  to  the  changes 
produced  in  tissues  and  organs  by  harmful  agents. 

Lesion  is  the  term  applied  to  any  structural  change  in  tissues  and 
organs,  no  matter  how  produced. 

Necrosis  means  death  and  may  be  used  to  indicate  death  of  any 
tissue,  or  of  a  single  cell. 

It  is  possible  for  injury  to  have  been  done  without  being  able  to 
demonstrate  it.  In  tetanus  and  rabies  it  may  be  impossible  to  demon- 
strate any  morphological  change,  even  though  the  reaction  is  most 
violent.  Thus  it  is  seen  that  inflammation  is  not  necessarily  a  local 
reaction. 

The  Reaction.— The  reaction  to  an  injurious  agent  is  the  most  interest- 
ing. This  reaction  naturally  varies  very  considerably,  and  this  depends 
on  the  amount  and  nature  of  the  injurious  agent  and  on  the  severity 
of  the  injury.    It  may  be  evidenced  in  three  ways: 

I.  By  chemical  changes,  as  alteration  in  secretion  or  excretion. 
II.  By  morphological  changes,  as  the  presence  of  serum,  fibrin  and 

proliferated  cells. 

III.  Physiologically,  by  alteration  in  functional  activity. 

As  already  stated,  the  object  of  the  reaction  is  to  get  (a)  rid  of  the 
injurious  agent,  if  it  is  still  present;  (6)  to  neutralize  its  action;  and 
(c)  to  repair  the  injury  which  has  taken  place. 

The  chemical  and  physiological  changes  are  usually  less  prominent 
than  the  morphological  changes.  The  changes  in  the  blood  folloAving 
poisoning  by  illuminating  gas  is  a  good  example  of  the  chemical  change. 
The  convulsions  produced  in  poisoning  by  strychnine  illustrate  the 
physiological  changes. 

Inasmuch  as  the  morphological  changes  are  most  frequently  seen 
and  have  been  the  most  thoroughly  studied,  this  phase  of  the  subject 
can  be  studied  to  advantage. 

The  morpJioloqical  changes  (which  are  partly  chemical)  which  take 
place  in  tissues  following  an  injury  are  as  follows: 
I.  Circulatory  disturbances. 

II.  Inflammatory  exudation. 

The  Circulatory  Disturbances. — These  occur  in  the  following  order: 

1.  A  momentarj^  spasm  in  the  bloodvessels,  when  the  irritant 
first  acts. 

2.  Dilatation  of  the  vessels  with  a  more  rapid  flow. 

3.  The  vessels  still  further  dilate  and  become  engorged,  but  the 
flow  decreases,  and  may  even  stop  in  some  of  the  cai)illaries  and  veins. 
The  leukocytes  become  attached  to  the  walls  of  the  veins. 

4.  'J'he  transmigration  of  the  leukocytes. 

These  cells,  especially  the  polynuclear  iform,  have  been  called  the 
soldiers  of  the  blood,  for  they  rush  to  the  seat  of  injury  and  slowly 


SYMPTOMS  OF  INFLAMMATION  163 

but  surely  j^ass  through  the  vessel  wall  into  the  tissues  (ameboid  move- 
ment) and  invade  the  masses  of  bacteria,  or  surround  the  irritant  if 
non-bacterial,  and  attempt  to  destroy  them.  These  cells  themselves 
are  killed  in  great  numbers  by  the  actions  of  the  product  of  the  bacteria, 
namely,  the  toxins. 

The  endothelial  leukocytes  appear  later  in  the  inflammatory  pro- 
cess, when  the  polynuclear  forms  are  diminishing  in  number,  acting 
as  a  sort  of  reserve  guard.  They  accumulate  to  counteract  the  toxins 
of  the  bacteria  and  to  attend  to  foreign  bodies,  carbon  and  free  fat. 
These  cells  destroy  certain  forms  of  bacteria  by  enveloping  them  in 
the  cell  structure.     Phagocytosis  is  the  term  used. 

The  lymphocytes  are  seen  most  abundantly  after  the  inflammation 
has  existed  for  some  time,  and  are  quite  characteristic  in  what  we 
know  as  chronic  inflammation. 

Symptoms  of  Inflammation. — While  these  changes  are  taking  place 
in  the  tissues,  certain  symptoms  of  the  inflammatory  process  have 
appeared,  of  which  the  patient  is  very  conscious.  These  symptoms 
are  four,  to  which  a  fifth  is  sometimes  added.  They  have  been  called 
the  cardinal  sig)is  of  inflammation  and  are  classic.  These  are:  Rubor; 
calor;  tumor;  dolor;  the  fifth,  functio  laesa;  translated  these  are:  red- 
ness; heat;  swelling;  pain,  and  impaired  function. 

1.  The  redness  is  due  to  the  increased  flow  of  blood.  Hyperemia  is 
the  term  that  is  sometimes  used  to  distinguish  the  early  stage  of 
inflammation.  As  the  flow  begins  to  decrease,  the  color  begins  to 
become  bluish  in  appearance. 

2.  The  local  heat  at  the  site  of  the  inflammation  never  exceeds  the 
temperature  of  the  internal  organs,  although  it  may  be  above  the 
normal  temjierature  of  the  part.  No  heat  is  produced  in  the  affected 
area.  The  increased  temjieratin-e  is  due  to  the  increased  rapidity  of 
circulation  and  to  the  increased  volume  of  blood. 

3.  The  sivelling  is  produced  by  the  exudation  from  the  blood- 
vessels. 

4.  The  j^aii^'  is  due  to  pressure  on  the  nerves  by  the  exudates.  It 
is  often  possible  to  count  the  heart  beat  by  the  exacerbations  of 
pain.  The  pain  is  most  severe  in  dense  structures,  especially  when 
the  inflammation  is  confined  in  bony  walls,  as  in  the  pulp  of  a  tooth. 
This  pain  is  sometimes  referred  to  a  point  distant  from  the  seat  of 
trouble,  as,  for  example,  earache  in  case  of  pulpitis. 

5.  The  disturbance  of  function  is  especially  seen  in  the  effect  on 
secretions,  which  many  times  are  prevented  or  suppressed.  Also 
movement  may  be  limited,  as  seen  in  stifl^ness  in  a  joint  that  is 
inflamed. 

The  Inflammatory  Exudate.^ — Associated  with  or  following  closely 
after  the  transmigration  of  the  white  cells,  there  is  an  exudation 
of  lymph  from  the  lymph  vessels,  the  purpose  of  which  is  to  neutralize 
or  to  reduce  the  chemical  activity  of  toxins  given  oft'  by  bacteria  or 
other  products  present  in  the  tissues.     The  exudation  of  lymph  is 


161  INFLAMMATION 

seen,  as  an  illustration,  in  a  mosquito  bite.  We  have  here  a  chemical 
poison,  and  we  get  all  the  changes  incidental  to  inflammation.  That 
is,  the  change  in  the  circulation;  the  increase  in  rapidity,  then  the  slow- 
ing down  of  the  blood  stream,  the  transmigration  of  the  leukocytes, 
and  finally  the  throwing  out  of  lymph.  This  is  a  small  inflamma- 
tion, but  it  has  all  the  phenomena  of  a  more  extensive  one. 

If  at  this  i)oint,  the  most  important  piu-pose  of  the  inflammatory 
reaction  has  been  accomplished,  namely,  to  counteract  or  neutralize 
the  agent  causing  the  injury,  the  inflammation  subsides,  the  early 
products  of  the  inflammatory  process  are  absorbed  and  the  tissues 
soon  return  to  a  normal  condition. 

Unfortunately,  however,  especially  where  bacteria  are  concerned, 
nature  is  not  always  successful,  and  other  phenomena  appear.  Further 
exudates  are  thrown  out;  the  exudation  becomes  more  complicated, 
and  other  substances  besides  the  lymph  are  thrown  out.  These 
e.vufhifrs  vari/  luider  different  conditions. 

Types  of  Exudation. — I.  Serous  e.viidaticm  is  watery  in  consistency, 
and  is  quite  similar  to  lymph;  in  fact,  it  resembles  it  very  closely,  and 
some  writers  simply  regard  the  serous  type  as  an  unusually  free 
exudation  of  lymph.  In  this  form  the  lymph  spaces  are  particularly 
in\-ol\-ed  and  the  swelling  is  known  clinically  as  edema.  This  is  seen 
sometimes  in  a  sprain.  Pressure  with  the  thumb  or  finger  over  the 
swollen  area  will  usually  leave  an  indentation,  wherfe  the  serum  has 
been  forced  out  of  the  tissues  by  the  pressure.  This  indentation 
gradually  disappears  as  the  pressure  is  removed  and  as  the  serum 
flows  in  again. 

Another  example  of  this  serous  type  of  exudate  is  a  blister  from  an 
ordinary  burn,  or  from  irritation,  or  friction. 

II.  Fibrinous  exudaiion  consists  of  leukocytes  and  the  formation 
of  fibrin  and  occurs  most  characteristically  in  the  form  of  a  membrane. 
A  good  illustration  of  this  is  the  membrane  formed  in  diphtheria. 

These  membranous  exudates  vary  in  their  characteristics.  Some  are 
firmly  adherent  to  the  underlying  tissues,  while  others  may  be  readily 
peeled  off,  leaving  sometimes  a  bleeding  and  sometimes  a  smooth 
surface. 

III.  Suppurative  exudaiion  is  the  most  frequent  and  most  impor- 
tant form,  and  is  characterized  by  the  formation  of  ])us.  This  is  the 
most  common  ending  of  acute  inflammation,  csjK'cially  when  bacteria 
are  acting  as  the  injurious  agent. 

In  the  discussion  of  inflammation  caused  by  bacteria,  it  was  shown 
that  leukocytes  were  clustered  together  and  the  lym])h  had  been  thrown 
out.  What  is  the  next  j)henomcii()n  to  a])])car?  It  is  briefly  that  the 
large  number  of  leukocytes  which  gather  in  the  tissue  form  an  ini])air- 
ment  of  the  nutrition  of  the  tissue  in  which  they  are  located;  and  we 
are  so  made  up  economically,  so  far  as  our  tissues  are  concerned,  that 
the  nutriment  sui)i)lied  to  the  tissue  is  not  sufficient  to  nourish  the 
tissue  itself  and  also  these  leukocytes,  with  the  result  that  the  tissue 


ABSCESS   FORM  AT  I  OX  165 

cells  themselves  lose  their  vitality;  and  then,  also,  the  leukocytes  in 
gi\'ing  battle  to  the  l)acteria  are  destroyed  in  large  numbers,  either 
by  the  bacteria  or  their  toxins.  This  lack  of  nutrition,  this  dying  of 
the  tissue  cells  in  which  the  inflammation  is  located,  and  the  death  of 
the  leukocytes  themselves,  cause  a  dissolution  of  the  tissue,  and  as  a 
consequence  there  is  a  cavity  filled  with  dead  leukocytes,  dead  tissue 
cells,  lymph,  and  dead  and  living  bacteria,  which  forms  a  creamy 
fluid  called  pus.    Clinically  this  is  known  as  an  ahsces.s. 

The  formation  of  an  abscess  marks  the  end  of  the  inflammation, 
so  far  as  the  tissues  themselves  are  concerned;  that  is,  the  inflamma- 
tory process  has  been  limited  and  localized. 

The  leukocytes  which  transmigrate  into  the  tissues  entirely  surround 
the  seat  of  injury  and  form  a  protecting  wall  against  further  invasion. 

If  it  were  not  for  this  action  of  the  leukocytes  in  forming  this  wall 
between  the  general  circulation  and  the  injurious  agent  in  the  form  of 
bacteria,  each  time  we  received  an  injury  infectious  in  its  nature, 
that  is,  of  bacterial  origin,  we  would  either  have  a  general  blood 
poisoning  because  injurious  products  would  be  taken  up  by  the  circu- 
lation, or  the  inflammation  would  extend  indefinitely  out  into  the 
tissues  until  our  bodies  were  wholly  consumed  by  the  inflammation. 
Therefore  this  formation  of  an  abscess,  while  disagreeable,  painful 
and  uncomfortable,  in  itself  is  an  excellent  thing,  because  it  prevents 
the  disturl)ance  from  becoming  a  general  one  of  very  serious  conse- 
quences. 

Occasionally  the  leukocytes  are  unable  to  control  the  local  action, 
or  perhaps  the  infection  began  in  the  circulation,  and  in  that  case 
general  blood  poisoning  or  .scptireinia  results.  This  is  a  very  serious 
condition.  But,  fortunately,  the  leukocytes  generally  form  an  actual 
resisting  force,  or  limiting  membrane,  through  which  the  bacteria  are 
unable  to  pass  and  inside  of  which  is  this  pus  cavity. 

The  next  question  that  naturally  arises  is,  what  becomes  of  the  pus 
and  this  wall  of  leukocytes?  The  tendency  of  all  abscesses  is  to  evacuate 
themsehes;  that  is,  to  tlu-ow  off  their  contents,  and  get  rid  of  the  secre- 
tion that  exists.  The  method  of  doing  this  is  as  follows:  the  fluid  ele- 
ments of  the  abscess  cavity,  or  the  pus,  increases  in  amount,  and  the 
increase  in  quantity-  increases  the  pressure  around  the  tissues,  and  as 
this  fluid  element  continues  to  increase,  the  pressure  becomes  greater 
and  greater,  and  as  the  pressure  becomes  greater  the  tissue  before  it 
gradually  yields,  and  the  pus  finds  its  way  in  what  has  been  classically 
called  the  pat/i  of  least  resistance.  This  act  of  nature  in  endea\'oring 
to  throw  off  the  pus  has  been  called  the  burrowing  of  pus.  It  tries 
hard  to  get  through  to  the  surface  of  the  body,  or  to  a  ca\'ity,  and  bur- 
rows its  wa\'  through  the  tissues  in  the  path  of  least  resistance.  When 
the  pus  has  finally  approximated  the  surface,  we  have  what  is  known 
as  pointing.  This  term  is  well  known.  Years  ago  it  was  customary 
to  poultice  any  inflammator\-  condition  to  bring,  as  they  said,  the 
trouble  to  the  surface,  and  this  poulticing  was  intended  to  hasten  the 


1 66  IN  FLA  MM  A  TION 

action  of  the  pus  burrowing,  to  hasten  the  pointing  of  the  abscess  so 
that  the  contents  could  be  evacuated. 

If  an  abscess  is  not  surgically  opened  and  the  pus  discharged,  the 
tissues  will  spontaneously  rupture  and  the  pus  will  escape,  either  on 
the  surface  of  the  body  somewhere,  or  else  into  one  of  the  cavities  of 
the  body,  as  has  been  suggested.  For  instance,  if  an  abscess  on  the 
lower  jaw  results  from  an  inflamed  tooth,  the  path  of  least  resistance 
may  be  downward  and  a  large  swelling  occurs  under  the  jaw.  As 
the  pus 'comes  closer  and  closer  to  the  surface  it  either  is  opened  and 
evacuated  surgically,  or  else  it  may  point  and  discharge  underneath 
the  chin.  If  there  is  an  abscess,  for  instance,  in  the  appendix,  and  it 
is  allowed  to  go  uncared  for  until  it  ruptures,  it  ruptures  into  the 
abdominal  cavity,  and  peritonitis  results.  The  pus,  in  other  words, 
tries  to  escape  from  the  tissue  and  come  out  freely,  and  thus  relieve 
the  pressure  on  the  tissues  in  which  the  abscess  has  formed. 

The  channel  tlu"ough  which  the  pus  passes  is  called  a  sinus,  and  the 
opening  on  the  surface  is  called  a  fistula.  These  two  terms  are  very 
common,  especially  in  inflammatory  conditions  connected  with  the 
mouth  and  teeth.  We  speak  of  a  sinus,  for  instance,  when  a  clironic 
abscess  discharges  into  the  mouth  over  a  tooth  on  the  gum.  The  canal 
or  channel  tlu-ough  which  the  pus  escapes  to  the  surface  is  the  sinus, 
and  the  opening  on  the  gum  out  of  which  the  pus  comes  is  the  fistula. 

If  the  abscess  is  a  very  superficial  one,  it  is  merely  a  simple 
abscess  of  the  skin.  When  the  pus  comes  through  the  surface  the 
layers  of  the  skin  may  be  destroyed,  leaving  more  or  less  of  an 
open  wound  of  a  very  superficial  nature.  This  condition  is  known 
as  an  ulcer. 

Chronic  Inflammation. — Before  discussing  repair  or  what  takes  place 
after  the  pus  is  evacuated,  chronic  inflammation  may  be  briefly 
described.  Chronic  inflammation  is  the  result  of  a  continued  irritation. 
It  may  follow  acute  inflamma;tion,  or  it  may  start  as  inflammation 
of  a  chronic  form.  Chronic  inflammation  is  a  very  different  process 
from  the  acute  form,  and  some  writers  have  gone  so  far  as  to  say  that 
chronic  inflammation  is  not  a  true  inflammation  at  all.  The  essential 
feature  of  chronic  inflammation  is  the  formation  of  new  connective  tis- 
sue, a  proliferation  of  the  fibroblast,  or  connective-tissue  ceH.  The  term 
fibrosis  has  sometimes  been  applied  to  this  form  of  tissue  change, 
l^ecause  it  describes  the  condition  better  than  the  term  chronic  inflam- 
mation. 

In  this  chronic  inflammatory  process,  hyperemia,  or  change  in  the 
bloodvessels,  that  is,  the  bringing  of  additional  blood  to  the  part, 
edema,  the  throwing  out  of  the  lymph,  and  su])punition,  the  formation 
of  pus,  are  absent.  Instead  there  is  this  proliferation,  as  it  is  called, 
of  the  connective-tissue  cell,  and  the  throwing  out  of  some  of  the  white 
cells  of  the  l)lood,  particularly  the  lymphocyte.  The  chief  character- 
istics, then,  are  the  formation  of  connective  tissue,  the  fibroblastic 
proliferation,  and  the  lymphocytic  infiltration  or  tlirowing  out  of  these 


REPAIR  167 

lymphocytes.  No  pus  is  foiiiul  nor  other  symptoms  of  the  inflam- 
matory changes. 

Repair. — Repair  is  the  general  term  userl  to  describe  the  processes 
taking  place  after  injury  and  exudation  caused  by  harmful  agents. 
The  repair  of  tissue  or  the  repair  of  the  injury  is  a  very  complicated 
subject  but  it  includes  three  di\'isions  which  will  be  briefly  described: 

Fird,  repair  includes  removal  of  foreign  bodies  of  all  sorts;  and  by 
foreign  bodies  is  meant  dead  cells  of  all  kinds:  (1)  tissue  cells  that  have 
died  as  the  result  of  the  process,  (2)  leukocytes  of  the  polynuclear 
form,  (3)  endothelial  leukocytes,  (4)  bacteria  dead  and  alive. 

The  absorption  and  removal  of  foreign  bodies  such  as  sutures  should 
also  be  included.  There  may  be  an  operation  and  stitches  are  taken 
deep  in  the  body.  These  stitches  are  allowed  to  stay  there,  and  they 
are  removed  as  foreign  bodies,  and  this  is  part  of  the  function  of  repair. 
In  addition,  secretions  from  bacteriological  products,  the  toxins,  and 
in  some  cases  the  lime  salts  which  are  formed  as  the  result  of  the 
various  conditions  are  included;  in  fact,  the  removal  of  anything  that 
is  foreign,  or  is  not  of  service  in  the  tissue  is  one  of  the  functions  of 
repair. 

Second,  the  organization  of  fibrin. 

Third,  the  regeneration  of  cells  to  restore  the  part  which  has  been 
destroyed. 

I.  How  does  the  removal  of  the  foreign  bodies  take  place?  In 
a  word,  the  leukocytes,  or  white  cells,  change  somewhat  their  function, 
and  they  become  active  in  carrying  off  the  foreign  bodies. 

These  dead  tissue  cells  are  destroyed  and  removed  inpart,  a  little 
at  a  time.  The  bacteria  may  be  actually  digested  by  the  leukocytes 
after  being  taken  up  by  these  cells.  Very  frequently  under  the  micro- 
scope these  endothelial  cells  may  be  seen  with  several  bacteria  in  their 
protoplasm.  The  endothelial  leukoc\i;e  is  especially  active  in  this 
part  of  the  process.    The  phenomenon  is  called  phagocytosis. 

II.  The  fibrinous  exudate  is  taken  care  of  by  the  connective-tissue 
cells,  the  fibroblasts,  which  form  and  grow  into  the  fibrin  and  gradually 
replace  it. 

III.  The  regeneration  of  cells  is  the  growth  of  new  cells,  and  is 
brought  about  by  what  we  know  as  cellular  division,  or  mitosis.  Under 
stimulation,  the  cells  in  the  vicinity  of  the  wound  will  gradually  begin 
to  multiply  and  fill  in  the  vacancy  that  is  caused  by  the  destruction 
of  the  tissue,  and  gradually  this  cavity  or  the  injury  due  to  the  loss 
of  tissue  is  replaced  by  new  cells,  which  have  divided  and  redivided 
and  divided  again. 

Clinically  speaking,  repair  or  the  healing  of  w^ounds  takes  place  in 
two  ways:  first,  by  primary  healing,  as  we  know  it,  called  healing 
by  first  inte7ition;  and,  second,  by  secondary  healing,  or  healing  by 
second  intention,  or  healing  by  granulation  tissue. 

Healing  by  First  Intention. — To  illustrate  the  healing  by  first 
intention,    let    us    assume   we   have   an   incised  wound.     After  the 


IGS  INFLAMMATION 

bleeding    is   stopped    the    wound,    which    is    the   result    of   a    cut, 
remains    filled    with    blood,   and    this   blood    coagulates    and    forms 
a  sort  of  plug  in  the  wound.     This  plug  or  coagulated  blood  retracts 
and  tends  to  hold  the  edges  of  the  wound  together,  and  over  the 
surface  a  crust  is  formed,  which  is  nothing  more  than  dried  secre- 
tion, dried  lymph  plus  a  few  cells,  and  this  is  commonly  spoken  of  as 
scab.     The  healing  process  begins  at  once.     Of  course,  the  various 
stages  of  inflammation,  the  changes  in  circulation,  and  throwing  out 
of  the  leukocytes  must  occur,  but  all  of  the  cardinal  s^'^mptoms  of  a 
true  inflammation  may  not  be  present.    In  addition  to  the  throwing 
out  of  the  leukocytes,  the  connective-tissue  cells  become  active;  and 
this  blood-clot,  which  has  been   mentioned  above,  acts  as  a  sort  of 
scaffolding,  upon  which  the   connective   tissue    builds,   sending   out 
little  prolongations  of  tissue.    This  connective  tissue  gradually  replaces 
the  blood-clot  and  the  edges  of  the  wound  are  held  firmly  together. 
Then  if  the  wound  is  on  the  surface,  the  epithelial   coverings   will 
send  out  prolongations  and  heal  it  over  with  no  evidence  of  scar.    If 
the  edges  of  the  wound  after  a  cut  are  held  firmly  together,  for  instance, 
with  plaster  or  a  bandage,  very  little  connective  tissue  is  formed.    It 
takes  very  little  new  tissue  to  repair  the  wound;  but  if  it  is  a  gaping 
wound,  more  material  is  needed  to  repair  it;  and  where  a  portion  of 
the  surface  of  the  skin  is  lost  and  it  becomes  impossible  for  the  epithe- 
lial cells  to  span  the  breach,  the  connective  tissue  fills  it  in,  and  the 
result  is  known  as  a  cicatrix.    The  tissue  which  forms  is  called  cica- 
tricial tissue,  or  scar  tissue.    This  has  a  very  great  tendency  to  contract. 
As  these  new  cells  become  older  they  contract  somewhat,  and  the  con- 
traction of  scar  tissue  is  well  known.     The  scar  tissue  that  results 
where  the  epithelium  is  not  completely  restored,  for  instance,  on  the 
liaud,  is  not  original  skin  tissue,  but  it  is  made  up  of  connective  tissue. 
Healing  by  Second  Intention.^ — It  has  been  shown  that  healing  b}^  first 
intention  has  nothing  to  do  with   infection;   that   is,  bacteria  have 
been  absent  in  the  changes  that  have  taken  place.     In  repair,  by 
second  intention,  however,  the  suppurative  process,  and  all  the  phe- 
nomena of  inflammation  with  the  formation  of  pus  and  the  evacuation 
or  tlu-owing  out  of  pus  cells,  and  the  products  of  exudation  must  occur 
before  the  actual  healing.     When  this  takes  place,  the  cavity  which 
results  from  the  ]>us  is  filled  in  gradually  by  granulation  tissue  and 
coiniectix'c  tissue  in  much  the  same  way  as  in  healing  by  first  inten- 
tion; but  there  is  much  more  tissue  to  be  restored,  and  the  healing 
process  may  be  slow,  jjarticularly  if  the  cavity  is  large.     It  is  often 
IKjssiblc,  after  the  pus  has  sjK-nt  itself  and  the  acute  symi)toms  have 
subsided,  to  bring  the  edges  of  a  wound  together  and  have  it  heal  by 
first  intenti(jn,  but  that  is  not  customary.     If  instead,  in  this  type  of 
wound  the  opening  is  packed  with  gauze,  and  allowed  to  fill  in,  as  we 
say,  from  the  bottom,  the  granulation  tissue  fills  up  gradually,  and 
each  day  less  gauze  is  used  in  the  ])acking  until  the  cavity  is  filled  in 
solidly   with    this   connective   tissue.     I'his   healing   by   granulation 


HEALING  BY  SECOND  INTENTION  169 

becomes  very  important  under  some  conditions,  })ecaiise  the  contrac- 
tion is  sometimes  excessive.  If  there  is  a  bad  inflammation  or  a  bad 
abscess  of  the  cheek,  for  instance,  or  the  cheek  muscle  and  the  wound 
has  to  be  repaired  by  second  intention,  or  by  granulation  healing, 
after  a  while  this  contraction  of  the  cicatricial  tissue  may  be  so  great 
that  the  person  is  unable  to  extend  the  lower  jaw,  or  open  the  mouth 
as  wide  as  desirable,  and  it  becomes  a  very  serious  condition  under 
some  circumstances.  Fortunately,  this  state  of  affairs  is  not  very 
common. 

Repair  then  in  general  is  the  effort  of  nature  to  restore  the  tissues 
to  the  normal  after  an  inflammation;  and  when  the  repair  is  complete, 
especially  if  it  is  by  first  intention,  the  parts  have  been  restored  to 
function  and  the  tissue  cells  resume  their  normal  relations. 

Note: — In  this  discussion,  liberal  use  has  been  made  of  the  masterly 
exposition  of  the  subject  by  Prof.  F.  B.  Mallory,  to  whom  the  author 
is  deeply  indebted. 


CHAPTER  VI. 
DEPOSITS  AND  ACCRETIONS  UPON  THE  TEETH. 

By  EDWARD   C.  KIRK,  Sc.D.,  D.D.S.,  LL.D. 

The  factors  involved  in  the  composition  and  mode  of  production 
of  deposits  and  accretions  upon  the  teeth  are  those  which  are  intimately 
connected  with  the  chemistry,  physiology  and  pathology  of  the  saliva, 
the  study  of  which  is  perhaps  one  of  the  most  important  considerations 
both  in  its  scientific  and  practical  aspects,  that  is  engaging  the  atten- 
tion of  the  dental  profession,  for  it  is  through  the  study  of  saliva  that 
we  hope  to  ultimately  solve  some  of  the  most  important  problems  with 
which  we  have  to  deal  in  dental  practice. 

It  has  been  mainly  through  the  study  of  the  saliva  that  we  have 
arrived  at  some  very  definite  ideas  as  to  the  causation  of  dental  caries, 
that  one  disorder,  the  prevalence  of  which  has  really  created  the  den- 
tal profession;  and  through  the  study  of  saliva  we  have  also  learned 
something  of  various  other  diseases  to  which  the  teeth  and  soft  tissues 
of  the  mouth  are  subject,  and  further,  we  hope  to  learn  something 
through  the  study  of  the  saliva  about  the  deposits  or  accretions  that 
are  commonly  spoken  of  as  tartar  and  about  their  mode  of  formation. 
After  all,  there  is  no  phase  of  dental  practice  that  is  of  more  immediate 
importance  to  those  who  are  pursuing  this  course  than  the  causes 
which  lead  to  the  formation  of  these  deposits  upon  the  teeth. 

As  for  the  word  "tartar,"  some  years  ago  in  one  of  the  popular 
magazines  there  appeared  an  article  by  a  physician  who  stated  that 
the  tartar  on  the  teeth  was  called  "tartar"  because  it  consisted  of 
tartrate  of  lime.  An  eminent  professor  of  chemistry  once  said  to  his 
class  during  a  lecture  that  he  never  had  understood  why  the  sulphate 
of  iron  was  popularly  called  copperas.  He  said  he  imagined  it  must 
have  been  called  copper  by  the  Dutch,  because  it  had  no  copper  in 
it.  By  the  same  mode  of  reasoning,  it  is  probable  that  this  medical 
man  called  these  deposits  tartar  because  there  is  no  tartaric  acid  in 
them. 

The  term  tartar  was  applied  by  the  alchemist  Basil  Valentine  to 
the  deposits  called  argols  in  wine  casks  consisting  essentially  of  potas- 
sium tartrate,  and  the  acid  derived  therefrom  was  called  tartaric  acid 
or  the  acid  of  tartaros.  Paracelsus  applied  the  term  much  more  widely 
to  include  earthy  deposits  from  animal  fluids  such  as  calculus  from  the 
saliva.  Tartar  consists  essentially  of  calcium  pliosphatc  or  phosphate 
of  lime  and  some  carbonate  of  lime  and  corresponding  magnesia  salts 
held  together  by  a  binding  material  that  we  call  mucin,  a  substance 
derived  from  the  mucus  of  the  saliva;  that  and  some  organic  matter 


DEPOSITS  AND  ACCRETIONS   UPON   THE   TEETH  171 

such  as  food  particles,  the  bo(hes  of  dead  or  dying  bacteria,  make  up 
the  bulk  of  what  we  call  "tartar." 

In  order  to  understand  the  formation  and  deposition  of  tartar  we 
must  first  know  something  about  the  saliva.  By  saliva  we  mean  that 
mucoid  fluid  which  we  find  in  our  mouths  from  time  to  time.  It  is  not 
always  flowing,  but  our  mouths  and  our  food  are  lubricated  and  mois- 
tened by  it.  This  saliva  is  manufactured  by  three  i)airs  of  glandular 
structures  situated  in  the  region  of  the  mouth  which  pour  their  secre- 
tions into  the  oral  cavity.  The  secretions  of  these  several  pairs  of  glands, 
which  we  speak  of  as  the  salivary  glands,  differ  in  their  composition. 
Neither  do  all  of  these  glands  pour  their  secretion  into  the  mouth  at 
the  same  time,  but  under  different  circumstances  and  in  response  to 
different  kinds  of  stimuli,  namely,  the  stimulus  of  food  or  the  stimulus 
of  the  thought  of  food  or  the  stimulus  of  pain. 

You  are  all  familiar  with  the  common  expression  that  if  we  think 
of  this  or  that  kind  of  food  it  makes  our  "mouths  water."  This  is 
literally  true.  I'nder  the  psychic  stimulus  of  the  thought  of  food,  espe- 
cially of  food  which  is  sapid  or  tasty,  the  salivary  glands  are  encouraged 
to  pour  their  secretions  into  the  mouth,  but  it  is  interesting  to  note 
that  different  kinds  of  foods  excite  the  secretion  of  different  glands. 
For  example,  the  physiological  chemist  Pavlow,  of  St.  Petersburg, 
found  that  when  a  piece  of  fresh  meat  was  offered  to  a  dog  the  flow 
of  saliva  from  the  sublingual  and  submaxillary  glands  was  stimulated, 
but  not  that  from  the  parotid,  which  is  a  large  gland  situated  in  front 
of  the  ear. 

When  dry  food,  like  powdered  meat,  was  offered  to  the  dog,  the 
parotid  salivary  secretion  was  stimulated.  So  under  different  stimuli 
we  find  a  response  from  different  glands,  and  the  response  seems  to 
stand  in  very  close  relationship  to  the  character  of  the  food  that  exerts 
the  stimulus.  This  is  an  important  relationship  too,  because  dry 
foods,  for  example,  need  a  great  deal  of  moisture  for  two  reasons: 
first,  for  converting  the  food  into  a  bolus  so  that  it  may  be  swallowed; 
second,  for  furnishing  sufficient  water  to  the  food  in  order  to  dissolve 
its  soluble  elements  and  to  give  taste  to  it.  Tasty  things  stimulate 
the  flow  of  saliva,  and  the  watery  secretion  of  the  parotid  gland  is 
necessary  in  order  to  dissolve  what  is  soluble  in  the  food  in  order 
to  bring  out  its  taste.  We  cannot  taste  anything  unless  it  is  soluble, 
no  more  can  we  smell  something  unless  it  gives  oil"  a  vapor  of  some  sort. 
So  that  gratification  of  the  sense  of  taste  is  secured  by  the  solvent 
action  of  the  parotid  saliva,  mainly,  upon  the  foods  that  we  take  into 
the  mouth. 

Besides  the  secretion  of  the  salivary  glands,  the  secretion  of  innumer- 
able mucous  glands  that  are  imbedded  throughout  the  whole  oral  or 
buccal  mucous  membrane,  the  lining  membrane  of  the  mouth,  is  added 
to  the  mixed  saliva,  and  it  is  the  secretion  of  these  mucous  glands 
that  give  to  the  saliva  its  slimy  or  slippery  quality,  owing  to  the  sub- 
stance mucin  contained  therein. 


172  DEPOSITS  AND  ACCRETIONS   UPON   THE   TEETH 

Mucin  is  a  very  important  constituent  of  the  saliva,  and  among 
other  things  has  a  very  direct  bearing  upon  tartar  formation,  but  its 
main  function  seems  to  be  that  of  a  hibricant.  Perhaps  you  all  know 
of  the  peculiar  technic  of  reptiles  when  they  feed.  A  boa  constrictor 
for  instance,  kills  its  prey,  which  may  be  a  half-grown 4)ig,  and  covers 
it  with  a  slimy  coating  so  as  to  lubricate  this  relatively  enormous 
mouthful,  and  to  render  its  passage  into  his  interior  as  easy  as  possible. 
In  a  minor  degree,  the  same  function  is  performed  by  the  lubricating 
exudate  of  the  mucous  glands  of  the  mouth  upon  the  bolus  of  food  in 
the  mouth  of  the  human  being. 

Beside  this  important  substance,  mucin,  the  saHva  contains  also  a 
peculiar  ferment  known  as  ptyalin,  the  function  of  which  is  to  begin  the 
digestion  of  starchy  substances  in  the  mouth.  Starch  as  such  is  not 
utilizable  as  food  by  the  body,  therefore  the  ptyalin  acts  upon  it,  con- 
verting it  by  degrees  into  a  kind  of  sugar,  maltose.  This  predigestion 
of  starch,  or  preparation  for  intestinal  digestion,  takes  place  in  the 
mouth,  hence  the  very  great  importance  of  thorough  mastication  of 
starches,  which  is  doubtless  the  main  justification  for  the  fad  of 
super-chewing  that  has  spread  over  the  country  under  the  name 
of  Fletcherism. 

Another  constituent  of  the  saliva,  though  perhaps  it  is  not  of  very 
great  importance,  has  been  exciting  a  great  deal  of  comment  in  the 
past  four  or  five  years;  that  substance  is  known  as  potassium  sulpho- 
cyanate,  ordinarily  spoken  of  as  sulphocyanate.  It  may  be  ques- 
tioned that  it  is  a  potassium  sulphocyanate,  but  some  kind  of  sulpho- 
cyanate is  present  which  is  possibly  a  sodium  or  ammonium  sulpho- 
cyanate. It  has  the  peculiar  property  that  when  to  a  small  quantity  of 
sali\'a  a  drop  or  two  of  a  test  solution  of  perchloride  of  iron  is  added, 
if  the  sulphocyanate  is  present  it  causes  a  red  or  reddish  colora- 
tion of  the  saliva.  This  is  rather  a  striking  reaction  which  can  be  made 
very  easily  by  simply  taking  a  few  drops  of  saliva,  a  half-thimbleful, 
adding  to  it  a  drop  or  two  drops  of  the  ordinary  tincture  of  chloride 
of  iron,  and  if  sulphocyanate  is  present  in  the  saliva,  a  red  color  will 
result.  This  reaction  is  rather  dramatic,  and  has  caused  a  great  deal 
of  discussion  and  debate  as  to  its  significance  which  thus  far  appears 
to  be  unimportant. 

Sulphocyanate  was  at  one  time  supposed  to  have  a  very  im- 
portant bearing  upon  caries  causation,  or  of  the  prevention  of 
carious  action  in  the  mouth,  but  recently  it  has  been  pretty  definitely 
shown  that  sulphocyanate  is  an  incidental  constituent  of  the  saliva,  and 
that  it  has  iio  very  important  significance  exccj)t  as  a  waste  ])roduct 
of  rmtrition  related  to  some  other  chemical  activities  in  the  body. 

In  arldition  to  the  constituents  mentioned,  saliva  collected  in  a 
receptacle  will  show  certain  sediments,  solid  matter,  if  it  stands  for  a 
short  tiiiK!.  The  salivary  scflimciit  consists  mainly  of  tlic  desquamated 
or  peeled-off  external  epithelial  cells.  Just  as  the  scarf-skin,  or  outer 
layer  of  the  cuticle,  separates  from  time  to  time,  so  does  the  mucous 


DEPOSITS  AND  ACCRETIONS   UPON   THE   TEETH  173 

nuMiibnine  of  the  mouth  sliecl  its  ei)ithelial  coatiiij^  into  the  saliva,  and 
we  find  mixed  with  the  saliva  these  epitheilial  seales  from  the  buccal 
m.ucous  membrane  which  when  a  specimen  of  sali\'a  is  allowed  to 
stand  for  a  time  separate  as  sediment. 

We  find  also  as  corpuscular  elements,  the  leukocytes,  or  white  blood 
C()ri)uscles,  which  <i;ain  their  way  into  the  saliva  chanfrino;  their  form 
somewhat.  They  ha\e  been  spoken  of  as  salivary  corpuscles,  l)ut 
they  are  really  white  blood  cells  which  have  undergone  certain  changes 
of  form. 

As  to  the  further  chemistry  of  the  saliva,  if  we  take  a  measured 
quantity,  and  evaporate  it  to  dryness,  we  find  a  small  residue  of  solid 
matter.  This  residue  consists  of  two  kinds  of  sul)stances,  certain 
mineral  salts  which  we  speak  of  as  the  inorganic  constituents  of  the 
sali\'a,  and  another  kind  of  solid  matter  which  is  organic  in  character. 

The  total  solids  of  saliva  ^'ary  considerably  in  amount.  It  is  difficult 
to  say  what  represents  the  total  quantity  of  solids  in  the  saliva,  but 
it  is  extremely  small  in  amount,  from  about  half  of  1  per  cent,  to 
possibly  1  per  cent,  of  the  total  saliva.  These  are  only  approximate 
figures,  because  the  composition  of  the  saliva  varies  constantly,  depend- 
ing upon  the  time  of  day  when  the  sample  is  taken,  how  closely  to  a 
meal,  whether  after  vigorous  prolonged  chewing,  after  drinking  large 
quantities  of  water,  or  after  abstaining  from  water  for  some  time. 
Saliva  becomes  more  concentrated  the  less  Avater  we  drink,  and  it  be- 
comes more  dilute  in  accordance  with  the  quantity  of  water  drunk. 
The  total  amoimt  of  solids  in  the  sali\a,  being  \ariable,  is  therefore 
rather  difficult  to  state. 

The  normal  saliva  in  the  ideally  healthy  individual,  who  has  no 
caries  of  the  teeth,  no  deposits  upon  the  teeth  and  in  whom  the  various 
functions  are  properly-  performed,  the  individual  who  is  living  up  to 
the  highest  state  of  physical  efficiency,  in  such  a  normal  human  being 
we  can  safely  say  the  saliva  is  colorless,  odorless,  and  tasteless. 

If  the  saliva  develops  either  an  odor  or  a  characteristic  taste,  or  a 
color,  something  is  wrong,  it  is  not  a  normal,  but  a  pathological  saliva, 
something  has  gone  wrong  with  the  individual,  the  chemistry  of  his 
body  is  not  working  properly. 

AVhen  studying  the  physical  appearance  of  a  quarter-  or  a  half- 
ounce  of  saliva  collected  in  a  test-tube,  we  find  that  in  addition  to  its 
limpidity,  its  clearness  or  opalescence,  a  slight  slimy  quality  due  to 
the  mucin  and  the  presence  of  sediment,  there  is  a  covering  of  froth 
upon  the  top  in  which  air  is  entangled.  Besides  which  the  saliva  con- 
tains dissolved  within  itself  a  certain  quantity  of  carbon  dioxid.  As 
we  give  off  carbon  dioxid  from  the  lungs,  so  carbon  dioxid  is  present 
to  some  extent  in  the  saliva,  and  it  gradually  escapes  on  standing; 
hence  the  saliva  in  the  test-tube  soon  loses  its  froth,  the  sediment  settles 
to  the  bottom,  and  we  have  a  column  of  this  clear,  odorless,  tasteless 
substance  above  a  layer  of  whitish  sediment. 

Any  variation  from  these  general  conditions  indicates  ill  health  of 


174  DEPOSITS  AND  ACCRETIONS   UPON   THE   TEETH 

some  sort,  or  some  error  in  nutrition,  and  the  saliva  is  so  sensitive, 
chemically,  it  reflects  the  variations  in  composition  of  the  blood  stream 
so  accurately  that  we  can  utilize  it  for  the  study  of  the  nutritional 
condition  of  the  individual  at  the  time  when  the  specimen  is  taken. 

It  is  a  familiar  fact  that  physicians  have  for  years  been  studying 
the  urine  and  the  blood,  as  means  for  determining  the  condition  of 
bodily  nutrition,  but  investigation  has  brought  forth  the  fact  that  the 
saliva  is  almost  as  important  an  index  of  the  condition  of  nutrition  for 
the  time  being  as  either  of  these  other  fluids  mentioned. 

When  the  saliva  is  poured  from  the  glands  into  the  mouth  it  comes 
into  an  entirely  new  environment,  that  is  to  say,  as  it  issues  from  the 
gland  it  is,  comparitively  speaking,  sterile;  it  is  not  infected  with  bac- 
terial elements,  we  do  not  find  the  bacteria  in  the  saliva  as  it  issues 
from  the  glands,  but  it  issues  into  a  cavity  that  is  infected  on  all  sur- 
faces; in  fact,  it  is  poured  into  that  portion  of  the  human  anatomy 
which  is  the  portal  of  entry,  for  nearly  all  of  the  bacterial  organisms 
that  enter  the  body,  and  the  saliva  is  necessarily  subjected  to  the 
influence  of  these  microorganisms. 

The  organisms  that  infect  the  mouth  are  not  only  myriad  in  number, 
but  they  are  of  an  infinite  variety  and  they  produce  different  effects 
upon  the  saliva.  Let  us  consider  a  little  more  closely  the  nature  of 
that  action  in  general.  It  is  a  familiar  fact  that  if  a  quantity  of  milk, 
for  example,  is  exposed  to  the  atmosphere  for  a  sufficient  length  of 
time,  especially  on  a  reasonably  warm  day,  the  milk  in  the  course 
of  time  undergoes  changes  and  becomes  sour,  as  we  say.  First,  it 
develops  a  sour  taste,  then  becomes  curdled,  and  if  it  is  left  to  stand 
still  longer  the  sourness  disappears  and  it  becomes  putrid,  developing 
a  very  disagreeable  odor,  as  it  undergoes  decomposition.  Modern 
bacteriology  has  settled  the  nature  of  these  processes.  They  are 
processes  of  decomposition  or  of  tearing  apart  of  the  various  complex 
compounds  that  we  find  in  milk  into  simpler  substances. 

IVIilk  contains  sugar,  nitrogenous  or  proteid  matter  in  the  form  of 
cheese,  or  casein,  it  contains  water  and  fats.  Each  one  of  these  sub- 
stances seems  to  have  a  selective  quality  for  certain  kinds  of  bacteria, 
some  of  which  attack  the  sugar,  for  example;  others  will  only  attack  the 
caseous  portion,  the  curd  of  the  milk;  other  germs  attack  the  fat. 
Butter,  for  example,  when  it  becomes  rancid,  forms  a  particular  kind 
of  acid,  butyric  acid,  as  it  is  called.  As  the  sugar  element  in  the  milk 
undergoes  decomposition,  it  becomes  sour  just  as  the  sugar  in  cider 
is  converted  into  vinegar,  or  alcohol,  as  the  case  may  be,  through  the 
agency  of  bacterial  action. 

rj)oii  the  same  ])rinci})l('  these  ^'ari()^ls  substances  in  the  saliva, 
nnicin,  animal  matter,  and  sometimes  sngar,  whicli  is  formed  l)y  the 
action  of  the  ptyalin  upon  starchy  matter  in  the  mouth  are  decomposed 
by  the  activity  of  certain  special  kinds  of  bacteria  and  produce  what 
are  designated  in  chemistry  as  typical  or  characteristic  kinds  of  end- 
products,   for  example,  acid  substances;  or  they  may  produce  ill- 


DEPOSITS  AND  ACCRETIONS   UPON   THE   TEETH  175 

smelling  substances,  hyrlrojifen  or  ammonium  sulphide  due  to  putre- 
faction or  substances  like  ])tomains  or  toxins  which  have  a  specific 
poisonous  action  ui)on  the  tissues  with  which  they  come  in  contact. 

Incidentally  caries  or  decay  of  the  teeth  is  produced  the  same  way. 
Thus  we  see  the  importance  of  the  study  of  the  saliva  in  relation  to 
the  manner  in  which  it  is  decomposed  through  the  agency  of  bacteria. 
From  all  this  we  may  also  deduce  the  immense  importance  of  a  clean 
mouth,  not  only  as  regards  the  integrity  of  the  teeth  and  the  tissues 
about  the  teeth  and  the  mouth  itself,  but  as  related  to  the  general 
health  of  the  individual.  The  question  of  a  clean  mouth  is  not  a  matter 
of  sentiment  alone,  or  a  matter  of  aesthetics,  but  it  is  fundamentally 
a  question  of  health. 

Since  decomposition  of  the  saliva  is  brought  about  through  the 
agency  of  a  large  variety  of  bacterial  forms  constantly  inhabiting  the 
mouth,  and  since  the  end-products  of  this  bacterial  action  are  so  varied, 
and  in  most  instances  either  poisonous,  or  capable  of  exerting  corrosive 
action  upon  the  tooth  structure,  it  is  evident  that  the  best  time  to  get 
rid  of  the  conditions  which  result  from  these  fermentative  and  putre- 
factive processes  that  take  place  in  the  mouth,  is  at  the  beginning,  and 
that  by  doing  so  we  can  successfully  prevent  not  only  diseases  of  the 
teeth,  but  many  diseases  which  affect  the  entire  body. 

In  connection  with  the  processes  of  decomposition  through  the 
agency  of  bacteria,  a  number  of  phenomena  manifest  themselves. 
In  the  first  place,  imder  certain  conditions  there  is  the  production  of 
a  peculiar  kind  of  deposit  upon  the  teeth  which  has  been  spoken  of 
as  the  bacterial  plaque.  The  bacterial  plaque  is  very  important  in 
many  ways.  In  the  first  place,  it  represents  the  first  step  in  the  pro- 
cess of  that  disintegration  of  tooth  structure  which  we  call  dental 
caries.  Broadly  speaking,  we  cannot  have  dental  caries  excepting 
through  the  agency  of  the  bacterial  plaque.  Viewed  simply  from  a 
physical  point  of  view,  a  bacterial  plaque  is  a  deposit  upon  a  tooth 
surface  which  localizes  the  process  of  decay.  The  function  which  the 
bacterial  plaque  performs  in  localizing  the  process  of  tooth  decay  at 
certain  points  is  the  factor  which  determines  the  principal  character- 
istic of  tooth  decay,  namely,  that  of  cavity  formation. 

Let  us  for  a  moment  e?jamine  the  nature  of  this  deposit  called  the 
bacterial  plac^ue.  Recall  for  the  purpose  of  this  argument  the  fact  that 
the  saliva  contains  first  of  all  mucin  in  solution.  In  order  to  have  a 
solution  of  mucin  in  the  saliva  we  must  have  an  alkaline  reaction  of 
the  saliva,  because  mucin  is  not  soluble  in  an  acid  fluid.  If  we  take  a 
specimen  of  saliva  and  add  a  drop  of  any  kind  of  acid  to  it,  acetic 
acid,  lactic  acid,  sulphuric  acid,  citric  acid,  etc.,  we  shall  immediately 
see  what  we  call  a  ])recipitate  which  looks  as  if  something  in  the 
saliva  had  been  cooked,  as  in  the  cooking  of  the  white  of  an  egg.  That 
happens  instantly  when  mucin  comes  in  contact  with  any  acid. 

One  of  the  acids  which  is  most  prompt  to  cause  the  precipitation 
of  mucin  is  lactic  acid,  the  acid  that  is  produced  when  milk  sours. 


176  DEPOSITS  AND  ACCRETIONS   UPON   THE   TEETH 

Lactic  acid  is  instantly  produced  in  the  mouth  by  the  action  of  cer- 
tain forms  of  bacteria  upon  sugars  found  in  or  taken  into  the  mouth. 

Sugars,  as  we  know,  are  produced  in  the  mouth  by  the  action  of  the 
ptyaHn  of  the  sahva  which  converts  the  starch  into  sugar.  As  long 
as  sugar  is  thus  formed  certain  classes  of  bacteria  act  upon  it  and  split 
it  up  into  lactic  acid.  These  lactic-acid-producing  organisms  being 
constantly  present,  fermentation  goes  on  and  lactic  acid  is  produced 
as  long  as  there  is  something  for  the  organisms  to  live  upon.  Just  the 
moment  that  a  point  (considering  a  bacterium  as  a  point)  of  acid 
production  is  set  up  in  the  saliva  there  occurs  a  precipitation  around 
that  point  of  insoluble  mucin,  and  when  the  action  is  started  by  the 
lodgement  of  lactic-acid-producing  organisms  upon  a  tooth  surface 
where  they  may  develop  and  multiply  undisturbed  in  protected  loca- 
tions the  process  continues  until  what  we  call  a  bacterial  plaque  is 
formed.  These  plaques  are  localized  upon  all  tooth  surfaces  that  are 
protected  from  the  friction  of  food  or  of  the  tongue  or  lips,  and  in 
places  that  are  not  kept  thoroughly  polished  and  clean,  especially  in 
the  class  of  mouths  that  are  susceptible  to  dental  caries. 

It  will  be  readily  understood  that  the  acid  which  is  manufactured 
at  the  ])oint  localized  by  the  bacterial  plaque  is  constantly  disinte- 
grating the  tooth  structure  upon  which  it  has  formed  and  breaking  it 
down.  Thus  we  have  a  deposit  produced  from  the  saliva  and  from 
conditions  existing  in  the  saliva  which  is  the  first  step  in  the  process 
that  we  speak  of  as  dental  caries. 

The  plaques  are  not  ordinarily  \'isible  to  the  naked  eye,  but  there 
has  been  introduced^  what  is  denominated  a  "disclosing  solution" 
containing  iodin,  which  renders  them  visible.  By  applying  tincture 
of  iodin  to  mucin  we  secure  a  color ,  reaction ,  that  is  to  say,  it  pro- 
duces a  brownish  or  reddish-brown  tint  deeper  than  that  of  the  iodin, 
especially  if  certain  of  the  sugars,  maltose,  for  example,  be  present. 
If  we  paint  the  tooth  with  iodin  or  spray  it  with  a  solution  of  iodin, 
in  the  course  of  time  we  will  find  that  the  iodin  has  stained  certain 
portions  of  tlie  tooth  to  a  darker  tint  than  others,  owing  to  the  fact 
that  the  plaques  have  taken  up  the  iodin,  combined  with  it,  and 
formed  a  dark  brownish  stain.  The  formula  of  Skinner's  disck^sing 
solution  is  as  follows: 

lodii)  crystals 50  grs. 

Potassium  iodic! .15  grs. 

Zinc  iodid .  .15  grs. 

Glycerin 4  dr. 

Water 4  dr.— M. 

As  an  adju\ant  to  the  disclosing  solution,  however,  another  stej)  or 
stage  has  been  suggested  by  II.  C.  Ferris,  and  that  is,  the  spraying  of 
the  surface,  after  it  has  been  treated  with  the  iodin  solution,  with  a 
boiled  starch  solution.     It  should  be  remembered,  however,  that  starch 

1  F.  H.  Skinner.  Dental  Cosmos,  1912,  p.  43. 


DEPOSIT  AND  ACCRETIONS   UPON   THE   TEETH  177 

and  iodin,  no  matter  how  they  are  put  tof!;ether,  j)ro(luce  a  very  dense 
blue  color,  and  unless  one  is  careful  in  making  this  test,  the  starch  may 
apparently  disclose  plaques  where  they  do  not  exist.  Hence  the  tooth 
should  he  rinsed  thoroughly  before  the  application  of  the  second  mem- 
ber of  the  disclosing  solution  is  made  in  order  to  remove  excess  of 
iodin.  As  a  matter  of  fact,  a  i)laque  is  disclosed  with  sufficient  clearness 
by  the  use  of  the  ordinary  official  standard  tincture  of  iodin,  7  per 
cent.,  without  subsequent  ai)i)lication  of  starch  solution. 

There  may  l)e  other  sources  of  plaque  formation,  })ut  the  explana- 
tion given  indicates  the  general  })rinciple  which  accounts  for  these 
soft,  slimy,  fairly  adhesive  deposits  upon  the  teeth,  which  can  be 
readily  rubbed  off  by  the  application  of  fine  pumice  on  an  orange- 
wood  stick,  if  the  rubbing  and  polishing  is  thoroughly  and  carefully 
done.  It  does  not  require  the  instrumentation  that  we  speak  of  as 
"scaling"  to  remove  deposits  of  this  class. 

In  the  precipitation  of  mucin  by  lactic  acid  we  have  the  general 
principle  involved  in  practically  all  of  the  deposits  of  that  character. 
These  may  be  localized  or  there  may  be  a  general  precipitation  of  mucin 
upon  the  teeth,  carrying  with  it  particles  of  food  or  debris  of  various 
sorts,  which,  if  not  removed,  condenses,  grows  harder,  more  tenacious, 
and  m.ore  difficult  to  remove,  though  when  first  deposited  it  is  very 
soft  in  character. 

We  come  now  to  a  consideration  of  an  entirely  different  class  of 
deposits  which  are  of  the  true  tartar  type,  namely,  the  mineral  deposits 
upon  the  teeth.  The  formation  of  tartar  is  a  most  complicated  process 
and  constitutes  one  of  the  puzzles  of  the  chemistry  of  the  mouth.  What 
we  do  know  about  it  is  this:  chemical  analysis  of  these  hard  deposits 
called  tartar  shows  them  to  consist  mainly  of  calcium  phosphate,  some 
calcium  carbonate,  the  bodies  of  dead  bacteria,  debris  of  food,  food 
particles,  all  bound  together  by  mucin. 

An  English  investigator,  ]\Ir.  Rainey,  about  fifty  years  ago,  under- 
took a  study  of  the  mode  of  formation  of  shells  of  various  sorts,  and 
he  was  lead  into  some  experimentation  with  reference  to  the  changes 
that  take  place  in  certain  kinds  of  earthy  precipitates  like  carbonate 
of  lime  under  varying  conditions,  as  for  example,  when  these  earthy 
substances  were  precipitated  in  a  solution  which  contained  a  ma- 
terial like  gelatin,  gimi  arabic,  or  egg  albinnen,  or  what  is  termed 
in  chemistry,  colloidal  substances.  He  found  that  the  carbonate  of 
lime  was  precipitated  from  a  watery  solution  in  a  more  or  less  crys- 
talline character,  but  if  the  smallest  quantity  of  glue,  albumin,  gelatin, 
or  other  glue-like  substances,  was  added  to  the  water  in  which  the 
precipitation  took  place  the  deposit  instead  of  being  of  a  crystalline 
character  was  made  up  of  little  spherical  bodies  that  were  more  or 
less  translucent.  The  precipitate  formed  very  slowly  and  this  investi- 
gator found  that  these  minute  globular  masses  side  by  side  tended  to 
increase  in  size  by  additions  to  their  exterior,  this  increase  in  size 
continuing  until  two  of  these  bodies  would  come  together  and  coalesce; 
12 


178  DEPOSITS  AND  ACCRETIONS   UPON   THE   TEETH 

then  another  one  would  grow  up  to  this  mass  and  they  would  coalesce, 
so  that  gradually  it  assumed  the  appearance  of  a  mass  of  marbles 
glued  together  or,  of  a  mulberry  mass. 

This  in^•estigation  led  others  to  continue  the  observations  and 
finally  it  was  shown  that  this  process  of  precipitation  and  molecular 
coalescence  was  at  the  bottom  of  a  number  of  very  important  processes 
not  only  in  the  human  body,  but  in  the  mode  of  growth  of  the  shells  of 
moUusks  and  the  pearl  formation  in  the  oyster,  for  example.  On 
further  investigation  it  was  found  that  the  pathological  conditions  that 
invoh'e  stone-like  concretions  in  the  kidney  or  the  bladder,  concretions 
of  a  calcareous  character  that  ate  found  sometimes  in  the  ear  and 
various  parts  of  the  body,  or  in  old  abscesses  that  have  undergone 
repair,  all  arose  after  the  same  principle  of  coalescence  of  the  pre- 
cipitate of  an  earthy  salt  in  combination  or  in  contact  with  a  colloidal 
or  glue-like  basis  which  acted  as  a  binding  material. 


Fig.  51. — Specimens  of  parotid  tartar;  actual  size. 

Precipitations  of  the  earthy  salts,  pho.sphates  and  carbonates,  that 
were  held  in  solution  in  the  sali\'a  when  they  take  place  in  the  human 
mouth  combine  with  the  glue-like  substance  in  the  saliva  which  we 
have  spoken  of  as  mucin,  and  are  bound  together  by  the  mucin  to 
form  the  mass  called  tartar  which  deposits  itself  upon  the  teeth. 
Tartar  \'aries  in  a  great  many  wa>s;  it  varies  in  the  rapidity  with  which 
it  forms,  it  varies  in  the  position  in  which  it  is  dei)()sited,  and  above 
all  it  varies  in  its  density,  the  tenacitx'  with  which  it  adheres  to  the 
tooth  surface  and  its  toughness. 

Certain  classes  of  tartar  undergo  very  raj)id  formation  and  enormous 
development.  Masses  of  tartar  weighing  as  nnich  as  from  two  hundred 
and  fifty  to  three  hundred  grains  are  reported.  It  seems  incredible 
that  any  human  being  could  tolerate  in  his  mouth  a  mass  of  tartar 
larger  than  a  pigeon's  egg  attached  to  the  buccal  surface  of  the  molar 
teeth,  yet  such  instances  are  by  Jio  means  infrequent.  Tartar  which 
is  formed  rapidly  and  in  large  masses  is  usually  relatively  soft  and 
friable  and  can  be  readily  removed  by  proper  instrumentation. 


DEPOSITS  AND  ACCRETIONS   UPON   THE   TEETH 


179 


Every  dentist  has  had  patients  with  the  idea  in  their  minds  that 
tartar  was  j^rotective  to  the  teeth  and  for  that  reason  they  objected 


Fig.  52. — Sublingual  tartar  on  a 
lower  incisor. 


Fig.  53. — Sublingual  tartar  on  a 
lower  canine. 


to  having  it  removed.  It  is  true  to  a  great  extent  that  teeth  upon  which 
that  kind  of  tartar  is  deposited  rarely  decay,  not  because  the  tartar 
is  protective,  but  because  conditions  that  cause  the  deposition  of  the 
tartar  are  precisely  the  opposite  of  those  that  favor  caries  of  the  teeth 


Fig.  54. — Partial  denture  clasped  to  first  and  second  molars,  which  have  been  lost  by 
deposition  of  parotid  tartar. 

When  such  enormous  accumulations  are  removed  from  the  teeth  the 
patients  are  often  surprised  that  the  teeth  do  not  come  out. 


180  DEPOSITS  AND  ACCRETIONS   UPON   THE   TEETH 

This  kind  of  tartar  will  form  upon  artificial  dentures  just  as  readily 
as  upon  the  surfaces  of  the  natural  teeth,  and  it  is  usually  found  at 
positions  opposite  the  orifices  of  the  ducts  of  the  salivary  glands. 
For  the  same  reason  we  find  these  enormous  masses  ordinarily  upon 
the  buccal  surfaces  of  the  molars  and  upon  the  lingual  surfaces  of  the 
lower  teeth  occupying  positions  almost  opposite  the  openings  of  the 
salivary  ducts.     (See  Fig.  54.) 

The  question  of  why  this  is  so  is  the  chemical  problem  that  we 
are  confronting.  This  is  what  we  know :  that  calcium  phosphate  as  it 
exists  in  tartar  is  not  the  same  kind  of  calcium  phosphate  that  exists 
in  solution  in  the  saliva;  that  is  to  say,  after  it  reaches  the  mouth 
it  undergoes  some  chemical  change,  the  nature  of  which  may  be  illus- 
trated as  follows:  One  of  the  popular  drinks  advertised  at  the  soda 
fountains  is  "Acid  Phosphate."  Calcium  phosphate  or  lime  phos- 
phate, chemically  speaking,  is  a  term  applied  to  a  group  of  compounds 
of  which  there  are  two  distinct  kinds.  One  contains  more  lime  in  pro- 
portion to  the  phosphoric  acid  than  does  the  other.  The  one  which 
contains  less  lime  in  proportion  to  the  phosphoric  acid  is  designated 
as  acid  phosphate,  which  is  soluble  in  water,  and  has  acid  properties; 
whereas  the  other  phosphate  which  is  designated  as  basic  phosphate 
contains  a  larger  proportion  of  lime  and  is  insoluble  in  water. 

If  we  add  to  the  acid  phosphate  a  little  more  lime,  we  convert 
it  into  basic  phosphate;  and  because  of  its  relative  insolubility 
it  would  fall  out  of  solution  as  a  sediment  or  precipitate.  A  similar 
process  occurs  in  the  deposition  of  this  phosphate  as  tartar  in  the 
mouth.  It  is  in  a  state  of  acid  combination  in  the  saliva.  Possibly 
it  is  the  content  of  carbonic  acid  in  the  saliva  which  holds  the  phos- 
phate in  solution,  and  when  the  carbonic  acid  escapes  in  the  saliva, 
the  phosphate,  having  nothing  to  hold  it  in  solution,  falls  down  as  a 
precipitate. 

Mucin  acts  as  a  glue-like  binding  material  to  the  small  earthy 
particles  of  phosphate  and  fastens  them  together  and  when  the  pro- 
portion of  mucin  to  the  calcium  phosphate  is  in  certain  ratio  the  mass- 
may  be  so  dense  and  adhesive  that  it  is  almost  impossible  to  cut  it 
with  a  steel  instrument  or  scrape  it  from  the  tooth  surface. 

The  escape  of  carbonic  acid  is  one  of  the  means  by  which  we  think 
the  earth\'  materials  of  the  sali\a  are  precipitated.  If  we  take  any 
alkaline  substance  into  the  mouth,  thereby  adding  free  alkali  to  the 
saliva,  we  are  likely  to  cause  a  precipitation  of  the  lime  salts. 

There  is  always  a  certain  amount  of  ammonia,  produced  by  the  chem- 
istry of  nutrition,  that  issues  from  the  lungs  with  the  expired  air,  and 
if  there  is  enough  ammonia  produced  in  a  given  case  to  im])art  a  definite 
free  alkalinity  to  the  saliva,  then  precipitation  of  the  lime  salts  takes 
place  or  ammonia  may  be  produced  in  the  mouth  by  putrefaction, 
decomposition  of  aniinjij  substances  causing  tartar  formation  in  unclean 
months. 

There  is  another  suggested  mode  of  tartar  formation.     Dr.  II.  II. 


DEPOSITS  AND  ACCRETIONS   UPON   THE   TEETH  181 

Burchanl  t'oiiiid  that  when  fermentation  is  going  on  in  the  mouth  with 
production  of  hictic  acid  in  small  quantities  the  mucin  is  j^recipitated 
and  the  coagulated  mass  of  mucin  tends  to  gather  within  itself  these 
earthy  salts,  just  as  a  net  going  through  a  stream  would  gather  up 
fish;  this  mass  is  deposited  upon  the  teeth,  and  coiulenses  more  and 
more,  forming  tartar. 

Tartar  has  l)een  thus  produced  artificially  out  of  the  mouth,  by 
taking  saliva  rich  in  calcium  salts  and  adding  small  quantities  of  dilute 
lactic  acid,  causing  precipitation  wlien  a  hard  material  of  a  dark  green- 
ish shade  is  produced,  physically  similar  to  the  deposits  that  we  find 
upon  the  teeth. 

One  of  the  most  interesting  examples  of  tartar  formation  is  that 
observed  upon  the  teeth  of  the  natives  of  Indo-China  and  the  Malay 
Archipelago.  They  are  habituated  to  the  chewing  of  the  betel  nut. 
This  use  of  the  betel  nut  as  a  masticatory  is  very  prevalent  throughout 
Indo-China  and  the  Malay  Archipelago. 

Habitual  chewing  of  the  betel  nut,  in  the  course  of  a  short  time, 
causes  the  teeth  to  become  stained  to  a  very  dark  reddish  brown  of 
about  the  color  of  the  exterior  of  a  chestnut,  and  enormous  deposits  of 
tartar  quickly  aggregate,  so  that  the  teeth  become  distorted  in  appear- 
ance and  position  and  are  very  quickly  lost  from  their  sockets.  It  is 
not  infrequent  that  young  people  not  over  twenty-five  years  of  age 
are  rendered  completely  toothless  by  the  habit  of  betel- nut-chewing. 

The  shavings  of  betel  nut  are  wrapped  up  in  pieces  of  the  leaf  of  a 
certain  kind  of  plant  called  Penang  pepper,  along  with  some  aromatic 
spices  such  as  catechu  or  cloves,  or  cardamom  seed,  according  to  the 
taste  of  the  betel-nut-chewer,  to  give  it  an  aromatic  flavor.  Then  about 
the  quantity  of  half  a  small  spoonful  of  lime,  made  by  burning  oyster 
shells,  is  sprinkled  all  over  this  mass  to  develop  the  flavor.  This  morsel, 
rolled  up  in  the  green  pepper  leaf,  is  very  carefully  tucked  away  in 
the  cheek.  It  causes  a  free  flow  of  saliva  tinged  with  a  red  color. 
The  addition  of  the  lime,  which  develops  the  flavor,  is  what  causes 
the  trouble.  The  acid  or  soluble  phosphate  of  lime  in  the  saliva  upon 
the  addition  of  this  extra  lime,  is  converted  into  the  insoluble  form  of 
phosphate  and  precipitated  on  the  teeth.     (Figs.  55,  56,  and  57.) 

The  foregoing  is  an  example  of  the  formation  of  tartar  due  to  change 
in  the  chemical  composition  of  the  lime  salts  of  the  saliva  from  a  soluble 
form  into  an  insoluble  form. 

The  hardness  of  the  tartar  depends  upon  the  amoimt  of  its  lime  con- 
stituent as  related  to  the  mucin  constituent.  The  hardest  formations 
of  tartar  contain  more  of  the  glue-like  or  mucinous  element  than  do 
the  more  friable  and  easily  broken-down  forms.  The  hardest  tartar 
formed  is  found  just  under  the  gum  margin.  The  large  masses  that 
are  attached  to  the  free  surfaces  of  the  teeth  opposite  the  ducts  of  the 
glands  are  usually  soft  and  easily  removed  regardless  of  size,  but  the 
rings  of  tartar  underneath  the  gum  margin,  the  hard  scales  of  tartar, 
are  the  most  difficult  of  removal.    It  is  this  kind  of  tartar  that  contains 


1S2 


DEPOSITS  AND  ACCRETIONS   UPON   THE   TEETH 


the  largest  proportion  of  organic  binding  material,  because  the  deposit 
of  tartar  at  that  point  sets  up  an  irritation  of  the  gum  tissue  and  causes 
the  weeping  out  from  the  gum  tissue  of  the  albuminous,  serous  portion 


i 

Fig.  55. — Lower  incisor  almost  completely 
encrusted  with  betel  tartar. 


Fig.  56. — Lower  canine  covered  with 
betel  tartar. 


Fig.  57. — Upper  and  lower  inci.sors  lost  from  deposit  of  betel  t;ut;ir.  As  they  grad- 
ually loosened  from  the  eiifroiichment  of  the  tartar  they  were  bcjuiid  together  with  fine 
brass  wire  by  a  native  dentist,  to  give  them  firmness  by  mutual  support. 


DEPOSITS  AND  ACCRETIONS   UPON   THE   TEETH  183 

of  tlie  blood  which  (•()inl)iiies  with  this  deposit  and  forms  a  very  hard, 
tenacious  mass. 

Fartlier  down  ui)on  the  roots  of  the  teeth  we  frecjuently  find  deposits 
of  another  form  of  tartar,  which  is  probably  not  salivary  in  origin. 
It  is  sjjoken  of'as  serumal  tartar  and  is  derived  from  the  serum  of  the 
blood.  From  a  chemical  stan(li)()int  it  is  i)ractically  a  formation  of 
the  same  character  but  it  originates  difi'erently.  So  far  as  we  know, 
this  serumal  tartar  which  is  situated  deep  down  upon  the  roots  of  the 
teeth  and  not  connected  with  saliva  in  its  origin,  is  the  result  of  some 
primary  infianunatory  condition  upon  the  tooth  root.  It  is  not  neces- 
sary to  go  into  the  causes  of  such  preceding  inflammatory  conditions 
which,  instead  of  breaking  out  as  abscesses,  have  healed  spontaneously 
by  what  w^e  call  the  process  of  resolution,  by  which  is  meant  that  the 
bacteria  which  set  up  the  inflammation  have  died.  They  have  been 
killed  by  the  resisting  forces  of  the  body  itself  and  the  inflammatory 
process  has  stopped,  and  the  tissues  have  undergone  repair,  but  the 
dead  bacteria  and  the  broken-down  tissue  constituting  pus  has  grad- 
ually- become  dehydrated,  and  there  is  left  a  cheesy  mass  which  later 
on  has  become  saturated  with  lime  salts  derived  from  the  blood  stream 
itself.  These  lime  salts  combine  with  this  cheesy  mass  resulting  in  a 
tartar-like  formation  in  which  the  cheesy  mass  of  colloidal  organic 
matter  takes  the  place  of  the  mucin  in  saliva  as  the  binding  material. 

Tartar  formed  in  that  way  is  a  mechanical  irritant  to  the  surround- 
ing tissues,  making  them  subject  to  subsequent  infections.  The  tartar 
acts  as  a  foreign  bod\'  in  the  tissue  setting  up  irritation,  infection  fol- 
lows and  the  process  is  repeated  with  continued  growth  of  tartar,  or 
the  abscess  may  break  at  the  gum  margin  and  a  pyorrheal  pocket  may 
thus  be  formed.  The  pus  pockets  in  pyorrhea  may  be  formed  from  the 
root  to  the  gum  margin  or  from  the  gum  margin  rootward. 

Two  other  phases  of  this  subject  are  of  importance;  one  is  the  color 
of  the  tartar,  the  other  is  the  solubility  of  the  tartar.  Tartar  we  find 
to  be  of  different  colors.  The  tartar  which  forms  rapidly  is  soft  and 
friable,  sali^'ary  in  origin  and  more  nearly  colorless  than  any  of  the 
other  varieties.  It  is  nearer  in  chemical  composition  to  a  simple  pre- 
cipitation of  phosphate  of  lime.  But  when  it  forms  slowly  and  under 
the  margin  of  the  gum  we  usually  find  it  highly  colored.  It  must  always 
be  remembered  that  tartar  precipitated  around  the  necks  of  the  teeth  is 
a  mechanical  irritant  to  the  soft  tissues  of  the  gum  region.  This  irri- 
tation predisposes  to  bacterial  infection,  which  leads  to  an  inflamma- 
tory process  and,  as  the  inflammation  proceeds,  more  or  less  blood 
weeps  out  from  the  irritated  tissue  in  contact  with  the  tartar.  The 
tartar  is  then  colored  by  what  we  call  the  hemoglobin  or  the  coloring 
matter  of  the  red  blood  corpuscles.  In  other  words,  the  color  of  the 
darker  varieties  of  tartar  is  derived  from  the  coloring  matter  of  the 
blood  which  undergoes  a  variety  of  changes  in  color  when  it  is  sub- 
jected to  the  preocesses  that  lead  to  its  decomposition. 

It  is  a  familiar  fact  that  a  black  eye,  or  any  black-and-blue  pigmen- 


184  DEPOSITS  AND  ACCRETIONS   UPON   THE   TEETH 

tation  of  the  skin  surface  due  to  a  bruise  is  at  first  red,  then  grows 
a  Httle  darker  because  the  coloring  matter  from  the  blood  has  weeped 
out  into  the  surrounding  tissues;  then  it  undergoes  chemical  decompo- 
sition, with  a  variety  of  color  changes,  until  it  becomes  very  dark. 
In  the  same  way  when  blood  oozes  out  from  the  gum  margin  and  comes 
in  contact  with  the  tartar  this  coloring  matter  is  absorbed  by  the 
tartar,  becomes  part  of  its  binding  material  and  undergoes  color 
changes  which  are  quite  analogous  to  those  observed  in  a  bruise,  that 
is,  from  a  reddish  or  brown  tint  through  a  variety  of  color  changes 
down  through  brown  and  blue  to  a  final  grayish  or  greenish,  almost 
black,  appearance. 

Tartar  may  be  pigmented  from  other  causes.  It  may  be  pigmented 
through  the  activities  of  certain  bacteria  that  are  color-producing,  or 
it  may  be  pigmented  by  the  character  of  the  food  or  other  material 
that  is  taken  into  the  mouth  as  in  the  case  of  the  betel-nut-chewer, 
or  as  in  the  case  of  tobacco-chewers  or  smokers. 

The  solubility  of  tartar  is  an  important  consideration  from  a  prac- 
tical point  of  view.  We  have  had  to  depend  thus  far  almost  altogether 
upon  mechanical  instrumentation  for  the  removal  of  these  deposits, 
for  the  reason  that  we  have  had  no  proper  solvent  for  this  material, 
something  that  will  disintegrate  it  without  endangering  the  texture  of 
the  teeth.  The  enamel  of  the  teeth  is  composed  of  the  same  mineral 
ingredients  as  tartar,  namely,  calcium  phosphate  and  a  little  carbonate. 
Therefore,  generally  speaking,  a  solvent  of  tartar  will  necessarily  also 
be  a  solvent  of  enamel,  and  it  is  a  very  difficult  proposition  to  apply 
a  solvent  to  the  tartar  without  damaging  the  teeth. 

There  are  instances,  of  course,  where  the  importance  of  the  removal 
of  tartar  in  certain  positions  may  warrant  that  risk,  if  the  solvent  is 
applied  intelligently  and  quickly  neutralized  if  it  tends  to  affect  the 
teeth  detrimentally.  But,  broadly  speaking,  the  chemical  problem  is  to 
find  something  that  will  dissolve  tartar,  but  will  not  dissolve  the  tooth 
structure.  We  would  be  safer  if  we  could  find  some  chemical  solvent 
that  would  dissolve,  not  the  calcium  phosphate,  but  the  binding  mate- 
rial that  holds  the  calcium  phosphate  together,  i.  e.,  the  mucin;  but  the 
calcium  phosphate  is  soluble  in  acid,  while  the  mucin  is  not.  Mucin 
is  soluble  in  alkali  while  calcium  phosphate  is  not  soluble  in  alkali,  at 
least  in  an\'  such  strength  as  can  be  borne  in  the  mouth.  So  we  are 
confronting  a  very  delicate  problem.  It  is  like  trying  to  use  a  germi- 
cide strong  enough  to  kill  bacteria  without  killing  the  individual  that 
is  infected  by  them;  to  find  an  agent  selective  in  its  action,  so  that  it 
will  damage  the  germ  and  not  damage  the  host  of  the  germ. 

Certain  substances  have  been  used  as  tartar  solvents  with  a  fair 
degree  of  success.  Lactic  acid  has  the  property  of  dissolving  the  cal- 
cium phosphate  and  of  forming  soluble  salts  of  calcium  phosphate  and 
may  be  a])i)lied  as  a  tartar  solvent.  It  is  not  a  vicious  acid  in  attack- 
ing the  tooth  structure,  and  may  be  ai)i)lied  to  remove  the  last  par- 
ticles of  tartar  after  tlic  bulk  has  been  removed  mechanically  by  instru- 


DEPOSITS  AND  ACCRETIONS   UPON   THE   TEETH  1S5 

mentation.  Solvents  shonid  not  l)e  used  for  the  removal  of  the  bulk 
of  tartar  deposits;  they  are  indieated  only  for  tiie  removal  of  the  last 
remnants.  It  should  never  he  forji^otten  that  all  the  other  pieces  of 
tartar  are  of  minor,  even  negligible  importance  as  compared  with  the 
last  piece.  A  man  may  walk  one  hundred  miles  aufl  take  many  thous- 
and of  steps  through  storm  and  weather  to  reach  his  home,  but  if  he 
does  not  take  the  last  step  over  the  doorway,  he  is  not  home  yet.  He 
may  die  before  he  lifts  the  latch.  He  has  not  reached  his  destination. 
All  his  previous  steps  coinit  for  nothing.  It  is  quite  the  same  with 
reference  to  the  removal  of  deposits.  It  is  not  all  those  that  have  been 
taken  ofi'  which  count.  It  is  the  last  one  that  counts,  and  when  that 
is  removed  the  work  is  done.  The  last  fragment  of  tartar  sometimes 
even  the  most  delicate  tactile  sense  may  fail  to  detect,  especially  if 
it  is  situated  down  toward  the  end  of  the  root  of  a  tooth,  or  in  a  pocket 
which  has  been  thoroughly  gone  over  with  the  instrument,  yet  one  is 
not  sure  whether  a  small  particle  has  not  been  left.  It  is  in  such  a 
place  that  we  may  have  recourse  to  the  use  of  a  solvent  such  as  lactic 
acid. 

Dr.  Joseph  Head,  of  Philadelphia,  has  promulgated  a  preparation 
known  as  "  Tartasol,"  which  is  said  to  be  a  solution  of  a  certain  percent- 
age of  acid  ammonium  fluorid.  I  have  had  no  personal  experience  with 
it,  but  it  is  said  by  its  inventor  to  have  the  desirable  selective  property 
which  we  have  referred  to,  that  it  will  dissolve  tartar,  but  not  tooth 
structure.  If  this  is  so,  it  should  be  a  very  useful  agent,  excepting  in 
certain  cases  in  which  it  is  reported  to  have  had  a  decidedly  irritant 
effect  upon  the  soft  tissues  aliout  the  teeth;  therefore  it  should  be  used 
with  discretion. 

A  word  should  also  be  said  about  the  solubility  of  the  bacterial 
plaque.  As  this  plaque  is  produced  mainly  by  precipitation  of  mucin 
by  acids,  it  is  perfectly  soluble  in  alkalies.  The  alkali  that  is  a 
natural  solvent  of  mucin  precipitated  by  acid  is  calcium  hydroxide, 
the  solution  of  which  we  ordinarily  speak  of  as  lime  water.  A  solution 
of  three  parts  of  lime  water  with  one  part  of  hydrogen  dioxid  has 
greater  efficiency  than  lime  water  as  a  means  of  removing  the  bac- 
•terial  plaque.  The  lime  water  renders  the  mucin  soluble  so  that  it 
can  be  washed  off  the  teeth,  and  the  hydrogen  dioxid  disintegrates 
the  placjue,  so  that  this  solution  has  a  doubly  favorable  action.  It 
should  be  used  habitually  as  a  dentifrice  by  all  patients  who  are  known 
to  be  constitutionally  susceptible  to  caries. 

The  sources  of  the  discoloration  of  tartar  to  which  I  referred  are 
also  the  sources  of  the  discolorations  that  we  find  on  teeth,  especially 
in  children,  which  are  spoken  of  as  green  stain  or  brown  stain.  There 
are  two  sources.  The  coloring  matter  of  the  blood  is  the  proteid  sub- 
stance called  hemoglobin.  When  in  solution  in  the  course  of  a  short 
time,  this  color  undergoes  a  change,  becoming  bluish  or  more  purplish 
in  color  as  the  hemoglobin  decomposes.  In  the  course  of  further  decom- 
position it  assumes  a  greenish  tint.    This  color  change  can  be  effected 


186  DEPOSITS  AND  ACCRETIONS   UPON   THE   TEETH 

much  more  quickly  by  adding  hydrogen  sulphide  to  the  blood.  Hydro- 
gen sulphide  is  produced  by  decomposition  of  albuminous  matter,  as 
in  the  decomposition  of  an  egg,  which  then  gives  off  that  peculiar  odor 
of  hydrogen  sulphide,  which  is  due  to  the  decomposition  of  the  sulphur 
elements  in  the  albumin,  and  it  is  the  hydrogen  sulphide  arising  from 
decomposition  of  the  albuminous  or  proteid  elements  of  the  blood 
acting  on  the  hemoglobin  that  changes  its  color  to  a  dirty  greenish 
tint. 

In  cases  of  irritation  of  the  gum  margin,  a  little  of  the  coloring  mat- 
ter of  the  blood  weeps  out,  putrefactive  changes  go  on  through  the 
agency  of  mouth  bacteria,  and  the  albuminous  portions  of  the  saliva 
and  the  blood  putrefies.  Hydrogen  sulphide  is  given  off,  the  sulphur 
compounds  unite  with  the  coloring  matter  of  the  blood  and  produce 
that  green  or  greenish-bro^vn  stain  observed  on  children's  teeth  and 
the  teeth  of  those  having  irritated  and  bleeding  gums  in  uncleanly 
mouths.  The  chemical  make-up  of  the  pigment  of  that  stain  is  the 
decomposition  product  called  sulphomethemoglobin.  The  children's 
teeth  upon  which  it  is  observed  are  not  properly  kept  clean.  They 
have  a  history  of  lack  of  practical  acquaintance  with  the  toothbrush, 
and  the  ordinary  technic  of  the  dental  toilet. 

Another  of  these  green  stains  is  in  all  probability  due  to  pigmenta- 
tions of  the  normal  covering  of  the  enamel  of  the  young  tooth,  which 
we  speak  of  as  Nasmyth's  membrane,  by  certain  color-producing  or 
chromogenic  bacteria  bringing  about  that  characteristic  color. 

By  treating  the  young  tooth  with  very  dilute  acids  we  can  isolate 
Xasmyth's  membrane  and  examine  it  under  the  microscope,  when  we 
find  it  permeated  with  what  looks  like  the  result  of  bacterial  activity. 

Both  these  types  of  green  stain  upon  the  tooth  surface  are  readily 
removable  by  the  application  of  iodin,  and  the  subsequent  use  of  polish- 
ing powders  or  pumice  applied  on  an  orange-wood  stick.  Iodin  is  not 
only  an  antiseptic,  but  also  a  bleaching  agent.  That  sounds  very  pecu- 
liar, because  it  stains,  but  we  can  stain  the  surface  structure  of  a  tooth 
to  a  deep  tint  with  iodin  and  simply  let  it  alone,  and  when  the  patient 
returns  the  next  day  that  tooth  will  be  much  lighter  in  color,  due  to 
the  bleaching  action  of  the  iodin.  We  need  never  be  afraid  of  perma- 
nently tinting  a  tooth  with  iodin,  unless  we  apply  it  with  a  steel  instru- 
ment, when  iodid  of  iron  is  formed  and  a  permanent  stain  will  be  pro- 
duced. Iodin  itself  may  be  used  with  perfect  freedom  upon  tooth 
surfaces  free  from  metallic  fillings  for  the  reason  that  it  is  ultimately  a 
bleaching  agent. 


CHAPTER  Vn. 
DENTAL  CARIES. 

By  EDWARD   C.  KIRK,  Sc.D.,  D.D.S.,  LL.D. 

Dental  caries,  or  as  it  is  commonly  designated,  tooth  decay,  is  a 
disease  which  is  practically  universal  in  its  distribution.  It  affects 
all  civilized  peoples,  some  uncivilized  tribes  and,  under  certain  con- 
ditions, even  some  of  the  lower  animals.  Xo  disorder  that  afflicts  the 
human  race  is  more  common,  as  it  has  been  shown  by  abundant  statis- 
tics that  from  85  to  95  per  cent,  of  civilized  human  beings  are  more 
or  less  the  victims  of  dental  caries  or  have  suffered  from  its  ravages  at 
some  period  of  their  lives.  Dental  caries  is  essentially  a  disease  of 
childhood  and  adolescence,  the  developing  individual  appears  to  be 
peculiarly  susceptible  to  its  invasion,  whereas  when  adult  life  is  reached 
the  tendency  to  tooth  decay  is  noticeably  lessened  so  that  in  the 
majority  of  cases  when  the  individual  has  reached  full  maturity  the 
progress  of  tooth  decay  appears  to  be  markedly  arrested.  So  manifest 
are  these  differences  in  the  activity  of  dental  caries  as  related  to  the 
age  and  development  of  the  individual  that  the  conditions  of  suscep- 
tibility and  immunity  to  the  disorder  are  accepted  as  characteristic 
of  its  activity.  As  further  evidence  of  the  same  characteristic  a  small 
proportion  of  individuals  are  found  to  be  quite  free  from  any  evidences 
of  tooth  decay,  never  having  suffered  from  its  invasion  at  any  time  or 
in  any  degree,  these  are  regarded  as  being  naturally  immune. 

The  period  of  childhood  and  adolescence  being  the  period  of  greatest 
susceptibility  to  dental  caries  makes  its  relationship  to  the  health 
of  children  of  school  age  one  of  \'ital  importance,  not  only  from  the 
hygienic  point  of  view  but  upon  educational  and  economic  grounds 
as 'well. 

Comparatively  recent  studies  of  the  question  furnish  abundant 
evidence  of  the  fact  that  the  prevalence  of  dental  caries  among  chil- 
dren of  school  age  is  the  fruitful  primary  cause  of  mental  backward- 
ness, interrupted  brain  development,  nervous  disorders,  errors  of 
vision  and  of  hearing,  bodily  malnutrition  and  a  host  of  evils  which 
not  only  retard  or  interfere  with  the  educational  process  but  impair 
the  physical  and  mental  efficiency  of  these  developing  citizens  of  the 
future  generation  to  a  serious  degree.  Hence  the  importance  of  not 
only  a  proper  understanding  of  the  nature  of  this  important  disorder 
but  a  clear  appreciation  of  its  gravity  as  a  menace  to  human  health 
and  efficiency. 

For  purposes  of  anatomical  description  a  tooth  is  viewed  as  having 


188 


DENTAL  CARIES 


a  crown  (corona)  which  is  all  that  part  of  the  tooth  exposed  beyond 
the  gum,  and  a  root  (radix)  or  radicular  portion  which  is  all  that  part 
of  the  tooth  embedded  in  the  bony  socket  or  alveolus  beneath  the 
gum.  The  portion  at  the  gum  line  between  the  crown  and  the  root 
is  designated  as  the  neck  (cervix)  of  the  tooth. 


Fig.  .58. — Vertical  section  of  a  tooth  'in  .silu  (l.j  diameters),  c  is  placed  in  the  puli> 
cavity,  opposite  the  cervix,  or  neck  of  the  tooth;  the  part  above  is  the  crown,  that  below 
is  the  root  (fang);  1,  enamel  with  radial  and  concentric  markings;  2,  dentin  with  tubules 
and  incremental  lines;  3,  cementum  or  crusta  petrosa,  with  bone  corpuscles;  4,  peri- 
cemental membrane:  5,  bone  of  mandible, 


Dental  caries  is  a  destructive  process  affecting  the  hard  dental 
tissues;  these  are  three  in  number:  (1)  the  enamel  which  is  the 
hard  outer  protective  cov^ering  of  the  underlying  dentin  of  the  tooth 
crown  and  (2)  the  cementum  or  crusta  petrosa  covering  the  dentin 
of  the  root;  and  (3)  the  dentin  which  forms  the  principal  body  of  the 


DENTAL  CARIES 


189 


tooth.  Within  the  body  of  the  dentin  in  the  central  cavity  of  the 
tooth  is  located  the  tooth  pulp,  a  soft,  highly  sensitive  and  vascular 
organ,  commonly  but  incorrectly  called  the  "nerve."  From  a  group 
of  specialized  cells  upon  the  surface  of  the  dental  pulp  there  radiate 
through  the  dentin  innumerable  fibers  of  living  matter,  richly  endowed 
with  sensation,  which  with  their  lateral  processes  ramify  throughout  the 
dentin  structure.  These  are  termed  the  dentinal  fibers  or  fibrillse,  and 
it  is  through  their  agency  that  we  perceive  the  painful  impressions 
arising  from  irritation  of  the  dentin  by  cutting,  by  heat,  cold,  sweets,  etc. 
Dental  caries  always  has  its  inception  upon  the  external  or  exposed 
surface  of  a  tooth;  it  never  arises  from  within  the  tooth.  For  a  long 
period  it  was  held  by  many  students  of  the  subject  that  tooth  decay 


Fig.  59. — Longitudinal  section  of  dentin  showing  distribution  of  dentinal  fibers 
and  stratum  granulosum.      (Miller.) 


was  an  inflammatory  process  similar  in  certain  respects  to  necrosis  of 
bone  and  those  who  accepted  that  view  also  held  that  caries  originated 
within  the  tooth  structure  and  gradually  progressed  outwardly  toward 
the  free  enamel  surface.  This  theory  was  maintained  by  some  until 
quite  recent  times,  but  its  fallaciousness  was  finally  completely  demon- 
strated by  the  researches  of  the  late  Prof.  Dr.  W.  D.  ^Miller,  published 
about  1880,  which  finally  gave  to  the  world  the  true  explanation  of  the 
process  of  tooth  decay. 

Briefly  stated.  Miller,  as  the  result  of  a  long  and  exhaustive  experi- 
mental study  of  the  subject,  found  that  the  destruction  of  the  hard 
structures  of  the  tooth  by  dental  caries  was  accomplished  through 
the  agency  of  a  certain  class  of  microorganisms  which  had  the 
characterivStic  function  of  fermenting  certain  of  the  sugars  and  con- 


190  DENTAL  CARIES 

verting  these  sugars  into  lactic  acid,  which  acid  in  its  turn  attacked  the 
soUd  structure  wherever  it  came  into  contact  with  it,  dissolving  out 
its  mineral  matter  which  caused  the  structure  to  disintegrate,  forming 
a  cavity  which  gradually  enlarged  until  it  eventually  included  the 
entire  crown;  indeed,  if  unchecked,  the  whole  tooth  may  in  this 
manner  become  disintegrated  and  lost. 

A  tooth,  however,  is  not  wholly  composed  of  mineral  matter  soluble 
in  lactic  acid.  If  we  immerse  a  tooth  for  a  sufficient  length  of  time 
in  an  acid,  for  example,  dilute  nitric  or  hydrochloric  acid,  it  will  be 
found  to  have  lost  all  of  its  enamel  covering  and  the  remaining  dentin 
and  cement  structures  while  still  possessing  the  general  conformation 
of  the  original  tooth  will  be  found  to  have  lost  their  hardness  to  such 
a  degree  that  the  structure  may  then  be  easily  cut  with  a  knife  into 
chips  or  slices  like  a  piece  of  cartilage  which  the  structure  now  closely 
resembles.  We  say  of  a  tooth  so  treated  that  it  has  been  decal- 
cified, that  is  to  say,  the  calcium  or  lime  salts  which  gave  to  the  tooth 
structure  its  characteristic  hardness  have  been  removed  or  dissolved 
out  by  the  acid  and  what  remains  is  an  organic  substance  or  animal 
tissue  called  the  organic  matrix  or  basis  substance  of  the  dentin  and 
cementum. 

The  relative  proportions  of  calcium  salts  or  mineral  matter  and 
organic  matrix  or  tooth  cartilage  in  the  dentin  and  enamel  structures 
are  shown  in  the  following  analysis: 


DENTIN  (Von  Bibra). 

Tooth  cartilage 27.61 

Fat 0.40 

Calcium  phosphate  and  fluoride        .      .       .  66.72 

Calcium  carbonate 3.36 

Magnesium  phosphate 1.18 

Other  salts 0.83 

ENAMEL  (Von  Bibra). 

Cartilage 3.39 

Fat 0.20 

Calcium  phosphate  and  fluoride        .       .      .      .89.82 

Calcium  carbonate 4.37 

Magnesium  phosphate 1 .  34 

Other  salts 0.20 


Organic  matter 
Inorganic  matter 

Organic  matter 
Inorganic  matter 


DENTIN 

(Kuehn). 

CaO 

53 

.42 

MgO 

2. 

,41 

P2O6 

39 

.46 

Fl. 

0 

,25 

ENAMEL  (Kuehn). 

CaO 53.75 

MgO 0.84 

P2O5 37.21 

Fl 0.29 

Organic  matter  and  H2O       8.48         Organic  matter  and   H2O     32.10 

Miller  showed  that  the  first  phase  of  the  carious  process  was  a 
dissolving  out  of  the  mineral  substances  or  decalcification  of  the  tooth 
structure  by  lactic  acid  produced  by  the  ferment  action  of  certain 
microorganisms  on  sugars.  He  further  showed  that  when  decalcifica- 
tion had  taken  place,  infection  of  the  exposed  organic  matrix  of  the 


DENTAL  CARIES  191 

tooth  structure  by  a  dift'ereut  type  or  class  of  microorganisms  occurred, 
these  latter  known  as  proteolytic  bacteria,  had  the  power  to  liquefy 
and  bring  about  putrefaction  of  the  organic  matrix  and  to  destroy 
it  in  the  same  manner  that  a  dead  animal  body  is  destroyed  and  disin- 
tegrated by  putrefactixe  changes.  These  two  phases  of  the  carious 
process  are  essentially  the  same  in  principle,  dependent  upon  the 
vital  activities  of  microorganisms  of  two  distinct  groups,  each  having 
the  power  to  decompose  certain  compounds  which  enter  into  the 
formation  of  tooth  structure  and  to  produce  by  their  action  certain 
characteristic  physical  phenomena  and  certain  end  or  decomposition 
products  equally  characteristic.  Thus  in  a  cavity  of  decay  the  presence 
of  acid  may  be  easily  demonstrated  by  bringing  into  contact  with  the 
decaying  mass  a  strip  of  blue  litmus  paper  which  will  at  once  turn 
red  where  the  decaying  mass  touches  it.  The  characteristic  odor  of 
putrefaction  is  readily  recognizable,  indeed,  ofl'ensively  so,  in  the 
breath  of  those  suffering  actively  from  tooth  decay.  This  odor  of 
putrefaction  arises  in  large  part  from  the  decomposition  of  the  organic 
matter  of  the  dentin  matrix  through  the  agency  of  the  proteolytic 
bacteria. 

The  human  mouth  is  not  only  the  portal  of  entry  for  many  disease- 
producing  microorganisms,  but  because  many  of  these  microscopic 
vegetable  organisms  thrive,  flourish  and  rapidly  reproduce  themselves 
under  the  conditions  of  moisture,  temperature  and  food  supply  that 
they  find  in  the  mouth  cavity  many  species  continue  to  inhabit  the 
mouth  and  those  which  are  possessed  of  disease-producing  dharac- 
teristics  become  the  agency  of  infection  by  which  a  variety  of  bodily 
diseases  are  produced.  An  unclean  mouth  is  therefore  a  constant 
menace  to  bodily  health  as  well  as  the  ordinary  source  of  tooth  decay. 
Fig.  60  shows  a  mixed  infection  of  various  bacteria  from  a  tooth  surface. 
•  But  though  a  great  variety  and  an  almost  infinite  number  of  micro- 
organisms are  constant  inhabitants  of  the  mouth,  and  though  the 
lactic-acid-producing  bacteria  which  cause  tooth  decay  are  found  in 
nearl}-  all  human  mouths,  it  is  well  known  that  many  teeth  do  not 
decay,  and  even  where  the  decay  process  is  active  not  all  surfaces  of 
the  teeth  are  equally  vulnerable  to  the  process  of  decay. 

It  has  long  been  noticed  that  certain  locations  or  areas  upon  the 
tooth  surfaces  are  more  lia})le  to  be  the  seat  of  decay  than  are  certain 
other  surface  areas.  In  general,  it  may  be  said  that  those  surfaces  of 
the  teeth  that  are  subjected  to  the  cleansing  action  of  friction  bv  the 
tongue,  the  lining  mucous  membrane  of  the  lips  and  cheek  surfaces 
or  teeth  surfaces  which  are  kej^t  free  of  bacterial  invasion  by  the 
friction  of  rough  or  fibrous  food  materials,  are  less  liable  to  decay; 
whereas,  those  surfaces  of  the  teeth  not  subject  to  the  self-cleansing 
action  of  the  foregoing  causes  are  most  likely  to  be  the  seat  of  decay, 
as  shown  in  Fig.  61. 

Locations  where  food  particles  infected  by  mouth  bacteria  can  find 
an  undisturbed  lodgement,  such  as  the  natural  pits  and  depressions  in 


192 


DENTAL  CARIES 


the  masticating  surfaces  of  the  molars  and  premolars,  the  sulci  between 
the  cusps,  and  especially  the  approximating  surfaces  of  the  teeth  which 
by  their  mutual  relations  of  contact  afi'ord  protected  areas  for  the 


Fig.  60. — Mixed  infection  from  tooth  surface.     (Williams.) 


^!^5^C 


Fig.  01. — Caries  localized   above   the   "contact   ijoint  "   on   the  approximating  surfaces 
of  contJKUOus  molar  teeth.      (W'illiams.) 


lodgement  of  food  jnirticles  and  its  undisturlx'd  decomposition  by 
lactic-acid-producing  bacteria  are  areas  which  in  a  suscej^tible  indivi- 
dual are  the  selected  locations  of  the  carious  process  (Figs.  62  and  63). 


DENTAL  CARIES 


193 


The  determination  of  the  location  of  tooth  decay  is  in  large  degree 
a  result  of  the  form  of  the  individual  tooth  and  of  the  relations  of  the 
teeth  to  each  other  in  the  dental  arches. 


Fig.  62.- — Beginning  caries  in  sulci  and  enamel  defects  of  morsal  surface  of  a  molar, 
also  showing  transparent  zone  of  Tomes.      (Miller.) 


\4^ 


\  / 


I'lu.   03. — Beginning  caries  on  approxinial  .surface.      (.Milk'r.J 

The  structure  of  the  tooth  itself,  that  is  to  say,  whether  it  be  hard 
and  dense  or  whether  it  be  relatively  soft  and  imperfectly  calcified, 
does  not  in  the  sHghtest  degree  influence  the  hability  of  teeth  to  decay 
13 


194  DENTAL  CARIES 

or  otherwise.  Any  tooth  will  decay  in  a  mouth  where  the  conditions 
causing  decay  are  active  and  no  tooth  will  decay  whatever  its  structure 
may  be  in  a  mouth  where  the  conditions  causing  decay  are  not  active. 
Or,  as  stated  by  the  late  Prof.  G.  \.  Black,  "decay  of  the  teeth  is  a 
factor  of  the  environment  of  the  teeth.  It  is  not  due  to  the  structure 
of  the  teeth  insofar  as  their  structure  is  characterized  by  density, 
hardness,  softness,  etc.  These  factors  may  influence  the  rate  of  decay 
but  they  do  not  determine  the  liability  to  decay." 

When  starchy  food  particles,  sugars  or  any  form  of  fermentable 
carbohydrate  food  material  is  lodged  in  contact  with  a  protected  area 
of  tooth  surface  it  becomes  subject  to  the  action  of  lactic-acid-produc- 
ing microorganisms  and  undergoes  fermentation  resulting  in  its  decom- 
position with  the  production  of  lactic  acid.  A  familiar  example  of  this 
process  is  the  souring  of  milk  when  left  exposed  for  a  time  to  the  air 
at  a  warm  room  temperature.  ]\Iilk  contains  a  considerable  quantity 
of  a  characteristic  sugar  called  sugar  of  milk  and  chemically  desig- 
nated lactose,  having  the  formula  C6H12O6.  Bacteria  from  the  air 
fall  into  the  milk  and  set  up  a  fermentation  of  the  milk  sugar  decom- 
posing it  or  splitting  it  into  lactic  acid  which  when  it  accumulates 
sufficiently,  gives  the  milk  an  acid  reaction  and  a  sour  taste.  The 
acid  thus  formed  breaks  up  the  combination  of  the  casein  with  the 
base  with  which  it  was  in  chemical  union  and  precipitates  the  casein 
as  a  curd  so  that  the  milk  becomes  thickened  and  when  separated  from 
its  watery  whey,  this  curd  is  the  material  from  which  cheese  is 
made. 

The  casein  or  cheesy  portion  of  the  milk  will  also  undergo  putre- 
facti^'e  changes  through  the  agency  of  proteolytic  and  other  forms  of 
bacteria  which  have  the  property  of  decomposing  this  type  of  organic 
matter  so  that  the  process  of  fermentation  and  subsequent  putre- 
faction of  milk  is,  in  principle  at  least,  quite  analogous  to  the  process 
of  tooth  decay. 

The  conversion  of  sugar  into  lactic  acid  by  the  fermentative  agency 
of  bacteria  is  represented  by  a  chemical  formula  as  follows: 

Glucoae.  liactic  acid. 

CeHiaOe  +  the  enzyme  of  B.  acidi  lactici  =  2C3H6O3 

that  is  to  say,  a  molecule  of  the  monosaccharid  glucose  is,  under  the 
actic)ii  of  the  enz.yme  of  the  B.  acidi  lactici,  si)lit  up  into  two  molecules 
of  lactic  acid.  Starches,  cane  sugar  and  the  more  complex  carbohy- 
drates must  first  undergo  changes  in  the  mouth  into  the  simpler  forms 
like  glucose  l)efore  they  can  l)e  split  into  lactic  acid  and  these  pre- 
liminary changes  are  brought  about  by  other  enzymes,  and  particu- 
larly by  ptyalin,  the  characteristic  ferment  of  the  saliva  which  pos- 
sesses marked  amylolytic  properties  or  the  power  to  convert  starches 
into  sugars  that  may  be  subsequently  broken  into  lactic  acid  by  the 
agency  of  the  j)roj)er  bacterial  enzyme. 


DENTAL  CARIES  195 

These  chemical  alterations  as  the  result  of  the  action  of  digestive 
ferments  and  bacterial  enzymes  upon  the  debris  of  food  substances 
are  constantly  goino;  on  in  mouths  which  are  not  kept  clean  and  free 
from  food  remnants  either  by  habitual  use  of  the  usual  tooth-cleansing 
devices  of  brush  and  dentrifices,  unless  we  may  exclude  those  excep- 
tional cases  which  are  naturally  self-cleansing  and  therefore  immune. 
It  is  this  constant  fermentative  activity  that  initiates  dental  caries 
wherever  on  a  localized  area  of  tooth  structure  it  is  permitted  to  con- 
tinue undisturbed. 

It  should  be  borne  in  mind  that  dental  caries  is  a  distinctly  localized 
process  in  its  inception.  The  disease  may  appear  in  one  or  many 
places  in  the  same  mouth,  at  the  same  time,  but  it  is  localized  in  the 
sense  that  it  does  not  attack  all  surfaces  of  the  teeth  simultaneously, 
nor  with  equal  impartiality.  Many  who  in  the  beginning  of  their 
study  of  the  pathology  of  dental  caries  have  clearly  grasped  the  fact 
that  lactic  acid  is  the  agent  which  initiates  the  disorder  by  dissoh'ing 
out  the  lime  salts  of  a  localized  area  of  tooth  structure,  and  that  the 
first  stage  of  cavity  formation  is  thus  explained,  not  infrequently 
jump  to  the  erroneous  conclusion  that  lactic  acid  alone  is  the  cause 
of  tooth  decay  and  cavity  formation. 

As  a  matter  of  fact,  a  generally  acid  saliva,  even  if  the  acidity  be 
due  to  lactic  acid,  will  not  give  rise  to  tooth  decay.  An  acid  saliva  is 
destructive  of  tooth  structure  by  bringing  about  a  general  decalcifica- 
tion of  the  teeth  which  is  manifested  m.ore  intensely  in  certain  locations 
than  in  others,  but  this  type  of  destruction  of  tooth  structure  is  not 
dental  caries  but  what  is  called  chemical  erosion  of  the  teeth,  a  disorder 
not  necessarily  dependent  upon  bacterial  activity,  as  it  may  be  pro- 
duced by  any  free  acid  formed  in  the  mouth,  exuded  into  the  mouth, 
or  taken  into  the  mouth. 

Dental  caries  is  a  characteristic  disease  with  a  well-marked  and 
definite  group  of  symptoms  and  within  certain  limits  it  has  a  known 
causation,  which  is  the  localized  destruction  of  the  hard  tissues  of  the 
tooth  by  the  solvent  action  of  lactic  acid  generated  at  the  point  of 
decay  by  the  agency  of  bacteria  acting  upon  carbohydrate  foodstuff. 

While  localization  of  the  decay  process  is  to  a  large  degree  deter- 
mined by  the  forms  of  the  teeth  and  their  relations  to  each  other, 
as  already  explained,  there  is  another  and  somewhat  complicated 
method  by  which  fixation  of  lactic-acid-producing  bacteria  to  a  tooth 
surface  is  brought  about,  a  method  which  because  of  its  importance 
in  relation  to  oral  hygiene  as  well  as  to  the  causation  of  decay  should 
be  clearly  understood  and  that  is  the  localization  of  decay-producing 
bacteria  upon  the  tooth  surfaces  by  the  precipitation  of  mucic  acid 
from  the  mucin  of  the  saliva  by  the  lactic  acid  set  free  by  the  activity 
of  the  bacteria  themselves. 

The  precipitation  of  the  mucic  acid  upon  tooth  surfaces  is  dis- 
cussed in  detail  in  the  chapter  on  Deposits  Upon  the  Teeth,  as  it  is 
a   result  of   bacterial   activity  responsible   to   a  considerable  degree 


196  DENTAL  CARIES 

for  the  formation  of  those  adhesive  deposits  upon  the  teeth  to  which 
the  general  designation  of  tartar  is  applied ;  it  is  important  to  recapitu- 
late its  main  features  here  insofar  as  they  are  concerned  in  localizing 
the  process  of  dental  caries. 

In  mouths  Avhere  caries  is  in  active  progress  the  saliva  is  ordinarily 
rich  in  mucin  which  when  present  in  appreciable  quantities,  is  recog- 
nizable by  the  glairy  or  ropy,  adhesive  character  of  the  fluid.  The 
sali^'a  has  the  property  of  viscosity;  it  has  a  certain  cohesiveness  and 
may  be  drawn  out  into  threads  of  greater  or  less  length  according  to 
the  quantity  of  mucin  that  it  holds  in  solution.  Such  saliva  is  nearly 
neutral  or  faintly  alkaline  in  reaction.  If  to  a  small  quantity  of  such 
a  saliva  gathered  in  a  test-tube  a  drop  of  lactic  acid,  or,  indeed,  any 
acid  is  added,  there  will  be  formed  at  the  point  of  contact  an  opales- 
cent precipitate  Avhich  is  the  mucic  acid  set  free  from  the  alkaline  base 
with  which  it  was  previously  in  chemical  combination  in  the  saliva 
as  mucin. 

If  the  test-tube  is  allowed  to  stand  undisturbed  for  some  minutes, 
the  precipitate  will  settle  to  the  bottom  of  the  glass.  The  precipitated 
mucic  acid  is  adhesive  and  insoluble  except  in  an  alkaline  or  saline 
solution.  If  now  we  apply  these  data  to  our  study  of  what  takes 
place  in  the  mouth,  we  shall  find  that  they  throw  much  light  upon 
the  mode  of  localization  of  the  carious  process. 

Assuming  that  in  a  susceptible  mouth  the  saliva  is  rich  in  mucin 
held  in  solution  by  the  alkaline  salts  of  the  saliva  and  that  the  mouth 
contains  carbohydrate  food  material  in  the  form  of  soluble  sugars, 
the  result  of  the  amylolytic  action  of  the  salivary  ferment  ptyalin 
upon  starchy  food  debris,  then,  in  such  a  mouth  infected  by  lactic-acid- 
producing  bacteria,  one  or  more  of  these  organisms  falling  upon  a 
tooth  and  temporarily  lodged  in  some  irregularity  of  the  enamel 
surface,  immediately  sets  up  a  fermentative  action  in  the  soluble 
sugar  in  its  salivary  environment  setting  free  lactic  acid  in  its  imme- 
diate vicinity.  The  liberated  acid  at  once  decomposes  the  dissolved 
mucin  of  the  saliva  throwing  down  the  adhesive  mucic  acid  in  con- 
tact with  the  body  of  the  microorganism,  cementing  it,  as  it  were,  to 
its  position  upon  the  enamel  surface.  Multiplication  of  the  bacteria 
proceeds  rapidly  and  the  process  of  acid  production  and  mucic  acid 
precipitation  proceeds  in  harmony  with  the  bacterial  multiplication. 
The  mass  of  bacteria  thus  organized  and  cemented  to  the  tooth  sur- 
face constitutes  what  is  known  as  the  bacterial  plaque,  the  essential 
factor  in  the  localization  of  tooth  decay  and  the  most  important  charac- 
teristic in  the  causation  of  the  disease.     (See  Fig.  64.) 

The  bacterial  plaque  presents  a  variety  of  physical  appearances 
under  the  microscojx'.  It  may  exist  as  a  small  glistening  semitrans- 
parent  mass  occu])ying  only  a  small  spot  of  the  enamel  surface  or  it 
may  present  the  aj)pearance  of  a  film  extending  over  a  considerable 
area,  in  fact,  over  all  surfaces  of  the  tooth  not  subject  to  friction  by 
food  or  the  tongue  and  buccal  mucous  surfaces.    The  microorganisms 


DENTAL  CARIES 


19- 


found  ill  the  plaque  are  never  a  pure  culture  of  lactic-acid  praducers 
but  while  these  are  presumal)l\'  always  present,  the  organisms  are 
usually  those  constituting  the  mixed  infection  usually  found  in  the 
unclean  mouth  (Fig.  (K)). 

It  has  been  shown  that  tooth  decay  is  brought  about  in  the  first 
place  by  the  decalcifying  action  of  lactic  acid  produced  by  the  ferment 
action  of  bacteria  upon  carbohydrate  food  debris.  This  is,  however, 
a  general  statement  of  fact  that  requires  somewhat  closer  analysis  in 
order  that  the  exact  nature  of  the  process  may  be  more  clearly  under- 
stood. All  carbohydrate  material  is  not  directly  fermentable  into 
lactic  acid,  thus  cane  sugar  and  starches,  two  important  nutritive 
substances,  must  undergo  certain  chemical  changes  in  the  mouth 
by  which  they  are  converted  into  simple  forms  of  sugar,  the  mono- 


FiG.  04. — Bacterial  plaque,  detarheil  from  enamel  surface  of  the  tooth  in  making  the 

preparation.      (Williams.) 


saccharids  having  the  general  formula  C6H12O6,  before  the  bacteria  of 
tooth  decay  can  con\'ert  them  into  lactic  acid,  this  preliminary  change 
called  hydration  or  hydrolysis,  is  brought  about  in  the  case  of  starches 
by  the  ferment  ptyalin,  an  enzyme  produced  by  the  salivary  glands 
and  which  is  therefore  a  normal  constituent  of  the  saliva.  Its  func- 
tion is  to  prepare  the  starches  and  possibly  some  of  the  more  complex 
sugars  for  later  assimilation  by  the  cells  of  the  body  in  the  process 
of  nutrition. 

The  physiological  chemist  Claude  Bernard  showed  by  experiment 
that  cane  sugar  as  such  is  not  assimilated  by  the  human  organism  when 
injected  into  the  veins,  but  when  taken  into  the  mouth  is  later  acted 
upon  by  a  special  amylolytic  enzyme  called  invertase  in  the  intestinal 
canal  and  is  thereby  converted  into  a  monosaccharid  assimilable 
sugar  suitable  for  the  nutrient  purposes  of  the  organism. 


198  DENTAL  CARIES 

The  typical  conversion  of  starch  and  of  cane  sugar  respectively 
into  lactic  acid  may  be  shown  chemically  as  follows: 

Cane  sugar. 
C12H22O11  +  H2O 

becomes  hydrolized  through  the  action  of  invertase  to 

Glucose. 
C12H24O12  =  2C6H12O6 

which  through  the  enzyme  action  of  B.  acidi  lactici  is  split  into 

4C3HI03      s-i^d  starch     C12H20O10       +        2H2O      becomes  hydrolized 
through  the  action  of  diastase,  or  ptyalin,  to 

Glucose. 
C12H24O12  =  2C6H12O6 

which  through  the  enzyme  action  of  B.  acidi  lactici  is  likewise  split 
into  '  • 

Lactic  acid. 
4C3H6O3 

From  the  foregoing  it  will  be  seen  that  the  mother  substance  from 
which  mouth  bacteria  produce  lactic  acid  is  a  simple  form  of  sugar 
belonging  to  the  monosaccharid  group  of  sugars  called  the  hexoses 
from  their  chemical  constitution,  all  having  the  formula  C6H12O6,  a 
compound  which  readily  splits  into  two  molecules  of  lactic  acid  having 
the  formula  2C3H6O3.  The  sugars  being  soluble  substances  readily 
diffuse  into  or  are  capable  of  absorption  by  the  bacterial  plaque  so 
that  the  bacteria  thus  fixed  and  localized  upon  a  protected  tooth  sur- 
face are  nourished  by  a  food  supply  of  soluble  sugar  directly  convert- 
ible into  lactic  acid  which  being  produced  continually  in  these  localized 
areas  of  bacterial  fixation  exerts  its  solvent  and  decalcifying  action 
upon  the  enamel  without  interference. 

The  manner  in  which  enamel  disintegrates  under  the  solvent  action 
of  lactic  acid  is  })oth  interesting  and  important.  The  enamel  covering 
of  a  tooth  crown  is  made  up  of  innumerable  prismatic  rods  or  prisms 
irregularly  hexagonal  in  section  and  densely  calcified.  These  enamel 
prisms  stand  endwise  to  the  dentin  and  pursue  a  radiating  and  some- 
times wavy  course  to  the  peripher^,'  or  free  enamel  surface.  The  prisms 
are  bound  together  by  a  material  of  much  the  same  chemical  nature 
as  that  constituting  the  prisms  themselves,  but  it  differs  therefrom 
in  the  physical  sense  that  it  is  more  readily  soluble  in  acids.  If  we 
take  a  thinly  ground  section  of  enamel  and  ))lace  it  on  a  slide  and 
while  examining  it  under  the  microscoj)e  allow  a  drop  or  two  of  dilute 
acid  to  act  upon  the  free  edge  of  the  specimen,  we  will  see  that  the 
acid  dissolves  out  the  interprismatic  cementing  substance  much  more 
rapidly  than  it  afl'ects  the  structure  of  the  prisms  themselves;  hence 


DENTAL  CARIES 


199 


the  acid,  because  of  this  greater  solubiHty  of  the  interprismatic  cement- 
ing substance,  tends  to  jjenetrate  between  the  prisms  separating  them 
from  each  other  and  causing  them  to  fall  apart  as  shown  in  Fig.  65. 

It  is  precisely  this  effect  that  we  see  in  the  opaque  chalky  white 
spots  that  make  their  appearance  upon  susceptible  tooth  areas  and 
which  the  intelligent  operator  recognizes  as  the  beginning  of  dental 
decay.  The  opacity  and  chalk\'  appearance  of  these  spots  is  due  to 
the  fact  that  the  interprismatic  cementing  substance  that  formerly 
gave  the  appearance  of  homogeneity  to  the  enamel  structure  has  been 
dissolved  out  leaving  air  or  fluid  in  its  place  having  a  different  refrac- 
tive index  than  the  enamel  (Fig.  06).  As  the  process  proceeds  the  area 
enlarges  and  the  enamel  rods  having  lost  the  means  of  mutual  sup- 
port, fall  apart  and  are  lost,  leaving  an  open  cavity  in  their  former 
location. 


Fig.  65. — Section  of  enamel  sulijected  to  the  action  of  dilute  acid  showing  solvent 
effect  on  the  interprismatic  cementing  svibstance  and  penetration  of  the  acid  between 
the  enamel  rods.     (Williams.) 

The  irritative  effect  of  the  gradual  penetration  of  acid  through  the 
enamel  in  the  process  of  tooth  decay  is  manifest  at  a  very  early  stage. 
Even  before  an  actual  cavity  has  been  formed  or  the  acid  penetration 
has  reached  the  junction  of  the  enamel  with  the  dentin,  the  latter 
tissue  will  have  manifested  its  reaction  to  the  irritation  by  recording 
certain  characteristic  changes  in  its  structure.  In  a  section  of  a  tooth 
attacked  by  slowly  advancing  caries  there  w'ill  be  noticed  in  the 
structure  of  the  dentin  lying  subjacent  to  the  line  of  invasion  a  cone- 
shaped  area  between  the  dentino-enamel  border  and  the  pulp  cavity 
with  the  apex  of  the  cone  toward  the  pulp  and  the  base  toward  the 
disinstegrating  enamel.  This  cone-shaped  area  of  dentin  is  more  trans- 
parent than  the  surrounding  dentin  structure  and  from  its  peculiar 
transparency  has  been  called  the  transparent  zone  of  Tomes,  from  Sir 
John  Tomes,  who  first  described  it.  Various  theories  as  to  the  cause 
of  this  alteration  in  the  character  of  the  dentin  structure  have  been 


200  DENTAL  CARIES 

advanced,  and  such  authorities  as  Tomes,  ]\Iagitot,  ]Miller  and  WalkhoflF 
regard  it  as  l)eing  an  o\'ercalcification  of  the  dentin  structure  as  a  result 
of  the  irritation  of  the  hving  matter  of  the  dentin.  Certain  it  is  that  it 
is  the  expression  of  a  vital  reaction  upon  the  part  of  the  dentin,  for  it 
does  not  occur  in  dead  {i.  e.,  pulpless)  teeth  and  it  always  does  occur 
from  long-continued  slight  irritation  to  the  dentin  from  whatever 
cause.  Its  main  importance  in  connection  with  the  study  of  dental 
caries  is  that  it  records  indisputablv  the  fact  that  dental  caries  in 
its  progress  sets  up  irritation  which  is  felt  and  recoi-ded  by  the  vital 
elements  of  the  tooth,  even  in  the  earliest  stages  of  the  disease  and 
before  the  integrity  of  the  enamel  surface  has  as  yet  been  seriously 
disturbed  (see  Fig.  02,  a). 

CARIES    OF   DENTIN. 

^Yhen  the  enamel  has  been  penetrated  and  a  cavity  has  thus  been 
formed,  invasion  of  the  dentin  rapidly  follows.  Caries  of  the  dentin 
differs  from  caries  of  enamel  in  two  important  particulars  arising  out 
of  the  differences  in  structure  and  composition  of  the  dentin  as  com- 
pared with  that  of  the  enamel. 

The  dentin  contains  a  relatively  larger  amount  of  organic  matter  than 
the  enamel ;  the  earthy  salts  entering  into  the  composition  of  the  dentin 
are  deposited  in  a  cartilaginous  substance  having  the  general  form  of 
the  tooth  and  known  as  the  organic  matrix  or  basis  substance  of  the 
dentin.  The  organic  matrix  which  in  the  formed  tooth  is  fully  calcified 
is  everywhere  permeated  by  fibrils  of  sensitive  living  matter  encased 
in  tubules  which  radiate  from  the  surface  of  the  pulp  through  the 
dentin  structure.  It  is  these  fibrils  of  living  matter  that  endow  the 
dentin  with  sensation  and  which  give  rise  to  pain  when  the  dentin 
is  cut  as  in  the  preparation  of  a  cavity  of  decay  preparatory  to  the 
filling  operation  or  when  sweets,  acids  or  other  irritating  substances 
are  brought  into  contact  with  the  walls  of  a  carious  cavity. 

The  distribution  of  living  matter  in  the  dentin  may  be  seen  from 
Fig.  59,  which  is  reproduced  from  a  photograph  of  a  section  of  the 
dentin  cut  in  the  plane  of  the  long  axis  of  the  tubules  in  which  the 
fibrillae  run. 

As  soon  as  loss  of  enamel  exposes  the  ends  of  the  dentinal  fibrillse 
invasion  of  the  tubules  by  the  bacteria  of  decay  promptly  takes 
place  and  the  tendency  of  the  carious  process  is  to  follow  the  direction 
of  the  tubules  toward  the  dental  i)ulp. 

^Yithin  the  dentinal  tubule  the  bacteria  of  decay  elaborate  their 
characteristic  lactic  acid  which  dissolves  the  sides  of  the  tubule  enlarg- 
ing its  diameter,  the  increased  space  being  promptly  packed  with 
organisms  reproduced  from  the  parent  pioneers  of  the  invasion  the 
dissolution  of  the  tubular  walls  continuing  until  the  area  of  decalcifica- 
tion involves  adjacent  tubules  which  have  been  undergoing  a  similar 
process  of  enlargement  until  coalescence  of  a  number  of  tubes  takes 


CARIES  OF  DENTIN 


201 


place  (Figs.  07  and  0(8).    Coincidently,  as  decalcification  proceeds  and 
exposure  of  the  organic  matrix  occurs,  that  structure  is  attacked  by  a 


Fig.  66. — Section  of  tooth  showing  locahzed  solution  of  interprisniatic  cement  sub- 
stance with  enamel  rods  standing,  constituting  the  "opaque  spot"  of  beginning  decay. 
(Miller.) 


Fig.  67. — Longitudinal  section  of  carious  dentin  showing  enlarged  tubules  packed  with 

bacteria.      (Miller.) 

group  of  bacteria  known  as  proteolytic  organisms  which  have  the 
property  of  elaborating  an  enzyme  that  brings  about  liquefaction  of 
the  cartilaginous  proteid  material  constituting   the  organic  matrix. 


202 


DENTAL  CARIES. 


Decomposition  and  putrefaction  of  the  decalcified  basis  substance  of 
the  dentin  thus  takes  phice  with  the  formation  of  so-called  liquefaction 


Fig.  68. — Cross-section  of  carious  dentin  showing  enlarged  tubules.     (Miller.) 


Fi<;.  ttO. — I.ifiuefaction  foci  in  carious  dentin.      (Miller.) 


foci  in  the  dentin   wiiich   liquefaction  foci   by  their  extension  and 
coalescence    idtimately    produce    what    is    commonly    known    as    a 


CARIES  OF  DENTIN  203 

cavity  of  tooth  decay,  the  process  couthiiiiiig  until  the  pulp  is  reached 
or,  if  the  process  is  not  arrested,  until  the  tooth  is  destroyed  (Fig.  09). 

It  has  already  been  noted  that  invasion  of  the  dentin  by  the  bac- 
teria of  caries  is  by  way  of  the  dentinal  tubules  which  these  organisms, 
generally  speaking,  follow  toward  the  pulp  and  various  considerations 
seem  to  indicate  that  this  mode  of  invasion  of  the  dentin  is  largely 
determined  by  the  fact  that  the  source  of  food  upon  which  the  organ- 
isms feed  is  found  in  the  substance  of  the  dentinal  fibril  or  the  juices 
of  the  fibril  itself. 

It  has  been  clearly  demonstrated  by  the  researches  of  jNIiller, 
already  referred  to  and  confirmed  by.  other  able  and  trustworthy 
investigators,  that  dental  caries  can  be,  and  is,  due  to  decomposition 
of  carbohydrate  food  particles  in  unclean  mouths,  from  which  we  have 
drawn  the  conclusion  that  tooth  decay  is  a  filth  disease,  that  if  proper 
care  as  to  oral  hygiene  is  instituted  and  maintained  that  dental  caries 
may  be  eradicated ;  in  short,  we  have  come  to  regard  it  as  an  accepted 
fact  that  "clean  teeth  will  not  decay."  This  conclusion  is  probably 
too  hastily  drawn  and  without  full  consideration  of  all  the  factors 
involved. 

Experience  shows  that  teeth  decay  more  rapidly  in  early  than  in 
adult  life,  that  the  teeth  of  some  individuals  decay  more  rapidly  than 
others,  that  the  teeth  of  some  never  decay,  that  many  who  give  scrupu- 
lous attention  to  their  teeth  are  extremely  susceptible  to  decay  of  the 
teeth,  while  others  whose  mouths  never  receive  any  attention  appear 
to  be  immune. 

The  problems  of  susceptibility  and  immunity  to  dental  caries  are 
as  yet  unsolved;  there  are,  however,  many  indications  that  give  color 
to  the  hypothesis  that  there  are  certain  nutritional  factors  that  have 
much  to  do  with  the  susceptibility  to  dental  caries  or  with  immunity 
therefrom.  Those  who  live  upon  an  excessive  carbohydrate  diet  are, 
as  a  rule,  found  to  be  more  prone  to  carious  invasion  than  those  whose 
diet  is  largely  of  a  proteid  character.  Probably  under  an  excessive 
carbohydrate  diet  the  percentage  of  sugar  in  the  blood,  normally  about 
0.001,  is  increased  and  if  the  salivary  fluids  and  the  juices  of  the  dentinal 
fibrils  derived  from  the  blood  reflect  this  increase  in  carbohydrate 
above  the  physiological  normal  would  readily  invite  the  invasion  of 
4ecay-protlucing  bacteria.  In  18S1  INIilles  and  Underwood  expressed 
the  opinion  that  the  bacteria  feed  upon  the  juices  of  the  dentinal 
fibrillse  in  dental  caries  as  follow^s:  "The  organic  fibrils  upon  which  the 
organisms  feed  and  in  which  they  multiply  are  the  scene  of  the  manu- 
facture of  their  characteristic  acids,  which  in  turn  decalcify  the  matrix 
and  discolor  the  whole  mass."^ 

If,  then,  susceptibility  to  tooth  decay  is  in  considerable  degree 
dependent  upon  a  constitutional  predisposition,  oral  hygiene  alone  and 
unaided  cannot  wholly  prevent  it,  although  it  can  undoubtedly  greatly 

'  Trans.  Seventh  International  Congress  of  Medicine,  London,  1881. 


204  DENTAL  CARIES 

diminish  its  ravages.  It  is  highly  probable  from  our  present  knowl- 
edge of  the  subject  that  complete  control  of  this  universal  disorder 
can  never  be  attained  by  local  measures  alone.  The  fundamentally 
important  question  of  dietetics,  of  food  habit,  must  be  studied  for 
what  light  it  can  throw  on  the  solution  of  the  problem,  for  even  now  the 
evidence  is  almost  overwhelming  that  the  inordinate  and  habitual 
use  of  sweets  by  civilized  children  is  a  custom  pernicious  alike  to  the 
integrity  of  their  dentures  and  to  their  general  health. 

Until  the  deeper  underlying  factors  of  the  causation  of  dental 
caries  are  discovered  we  must  rely  upon  the  means  at  our  command  in 
the  principles  and  art  of  oral  hygiene  to  protect  humanity  as  best  we 
may  from  the  scourge  of  dental  caries  and  its  consequent  damage  to 
health  and  life. 


CHAPTER  VIII. 
THE  TEETH  AS  A  MASTICATING  MACHINE. 

By  CHARLES   R.  TURNER,  M.D.,  D.D.S. 

An  analysis  of  the  reasons  for  preserving  the  teeth  gives  first  impor- 
tance to  their  preservation  that  they  may  perform  their  functions  as 
a  part  of  the  human  organism,  and  play  their  part  in  that  sum  total 
of  activities  which  go  to  make  up  the  physical  life  of  the  human  animal. 
As  so  much  attention  is  now  being  given  to  the  matter  of  tooth  conser- 
vation it  is  proper  to  be  informed  as  to  the  important  part  taken  by 
the  teeth  in  one  of  the  most  essential  of  the  distinctive  animal  functions, 
indeed,  one  which  is  necessary  to  the  preservation  of  life  itself.  Fur- 
thermore, it  is  one  of  the  dictimis  of  physiology  that  any  part  of  the 
body  which  ceases  to  perform  its  functions  atrophies,  or  the  character 
of  its  tissues  degenerates,  and  in  course  of  time  is  incapable  of  per- 
forming its  function;  and  so  the  duties  of  the  teeth  have  a  twofold 
interest  for  us. 

In  order  then  to  present  the  case  for  the  preservation  of  the  teeth, 
as  it  were,  something  must  be  said  about  their  functions  in  the  human 
body,  and  in  that  connection  as  a  machine,  or  as  a  part  of  a  machine, 
concerned  in  the  preparation  of  the  food  for  subsequent  stages  in  the 
digestive  process. 

To  appreciate  fully  the  part  taken  by  the  teeth  in  the  activities  of 
the  human  organism,  it  might  be  interesting,  and  it  will  certainly 
give  a  good  background  for  the  study  of  the  human  dental  mechanism, 
to  take  some  account  of  the  way  the  teeth  have  developed  to  perform 
their  present  functions. 

The  basal  functions  of  animal  as  distinguished  from  plant  life,  and 
as  fundamental  to  existence  itself,  are: 

1.  Alimentation. 

2.  Respiration  and  circulation. 

3.  Locomotion. 

4.  Reproduction. 

Evolution  of  Tooth  Forms. — In  the  simplest  form  of  animal  life,  as 
for  example  in  a  unicellular  body,  the  amcha,  we  have  the  process  of 
alimentation,  or  the  securing  of  nutrition,  an  extremely  simple  one. 
The  animal  is  afloat  in  the  water  and  extracts  its  nutriment  there- 
from, the  nutritive  elements  are  absorbed  through  the  cell  wall  and 
nutrition  is  effected  through  a  simple  process  of  osmosis. 

No  one  fact  so  impresses  the  student  of  zoology  as  the  relation- 
ship between  the  form  and  structure  of  the  various  parts  of  an  animal 
organism  and  the  functions  they  are  called  upon  to  perform.     It  is 


206  THE   TEETH  AS  A   MASTICATING  MACHINE 

very  interesting  to  note  the  adaptive  modification  of  the  structures  to 
changes  in  these  bodily  functions,  and  to  observe  how  they  have  been 
modified  during  the  various  stages  in  the  development  from  the  lowest 
organisms  up  to  the  highest  forms. 

As  the  scale  of  animal  life  is  ascended  and  a  multiplication  of  func- 
tion occurs  differentiations  of  tissue  appearing  here  and  there  are  found, 
which  occur  as  a  result  of  a  certain  function  falling  upon  that  tissue. 
Certain  cells  are  given  over  to  the  function  of  reproduction;  certain 
other  cells  or  collections  of  cells  are  specialized  for  locomotion,,  etc. 

In  some  of  the  lower  forms  of  animals,  before  the  vertebrates,  there 
is  a  simple  tube  like  a  channel  devoted  to  alimentation;  the  food  goes 
in  one  end  and  the  excreta  are  ejected  at  the  other.  There  is  no  special 
collection  of  cells  at  the  beginning  of  this  tube  to  prepare  the  food.  In 
the  coBlenterata ,  for  example,  the  alimentary  canal  is  not  separate  from 
the  general  body  cavity,  but  in  the  annidoida  and  annulosa  it  is  a 
distinct  tube. 

A  little  higher  in  the  scale,  as  in  some  of  the  insects,  the  crabs  and 
the  crustaceans,  there  are  at  the  beginning  of  this  alimentary  tract 
cells  which  are  concerned  to  some  extent  with  the  preparation  of  the 
food  for  its  passage  through  the  canal.  There  is  no  real  masticating 
apparatus,  however,  even  in  many  of  the  lowest  of  the  vertebrate 
animals,  but  the  first  thing  that  at  all  appears  like  it  occurs  in  some 
of  the  lower  fishes,  in  the  hag-fishes  and  in  the  lamjjrey  eels.  The 
latter  have  a  suctorial  mouth  which  they  attach  to  some  object, 
either  the  side  of  a  larger  fish  or  a  stone  covered  with  moss,  and  obtain 
their  nutrition  from  it  by  a  process  of  suction.  Inside  of  this  mouth  are 
layers  of  cells  which  are  rather  horn-like  in  character.  They  are  for 
the  purpose  of  imV)edding  themselves  in  the  substance  to  which  the 
mouth  is  applied  and  of  affording  a  firm  hold  so  that  the  animal  may 
draw  its  sustenance.  This  is  perhaps  the  very  simplest  type  of 
differentiation  of  tissue  for  this  purpose. 

In  the  vertebrate  animals  the  cells  constituting  the  tissues  at 
the  entrance  of  the  alimentary  canal  are  specialized  with  a  view  to 
assisting  in  the  process  of  either  securing  or  preparing  the  animal's 
food.  The  apparatus  is  simple  in  the  less  highly  developed  orders  and 
becomes  a  more  complicated  instrument  as  the  scale  is  ascended.  The 
food  convenient  to  the  animal  or  required  by  it,  and  the  food-reducing 
mechanism  are  in  constant  correspondence.  Out  of  this  necessity 
has  developed  teeth.  The  teeth  have  developed  in  accord  with  and 
to  meet  the  needs  of  the  food  which  the  animal  utilizes.  They  are 
corneal  or  horn-like  in  some  of  the  lower  orders  and  as  we  go  upward 
they  become  calcified.  They  are  simple  cones  or  they  are  modified 
under  certain  conditions  to  forms  which  serve  better  their  functions. 

Fishes  arc  the  lowest  vertebrate  type  that  have  calcified  teeth;  they 
arc  simply  calcified  cones  arranged  around  the  border  of  the  jaws 
and  serve,  to  hold  tiie  food.  Some  of  the  teeth  are  recurved  and  serve 
like  the  l)arb  of  a  fish-hook  to  prevent  the  escape  of  the  prey  (Fig.  70j. 


EVOLUTION  OF   TOOTH  FORMS 


207 


Of  the  amphibians  some  have  no  teeth,  as  the  toad,  while  others,  such 
as  the  frog,  have  teeth  not  iinhke  those  of  fish,  at  least  always  in  the 
uj)per  jaw  for  the  hiUfroq  has  no  lower  teeth. 

Of  the  reptiles-  many  have  teeth.  The  lizards  eat  butterflies,  worms, 
insect  larvae,  etc.,  while  i'^aAr*  live  on  am])hibians  and  their  larva^  and 
fish,  and  the  I'ijjerine  snakes  on  small  mammals.  Crocodiles  and  turtles 
eat  fish,  small  amphibians  and  insects.  The  snakes  do  not  chew  their 
prey  but  swallow  it  whole.  The  lower  jaw  is  jointed  in  the  center  and 
articulates  with  the  skull  through  the  quadrate  bone,  thus  allowing 
the  mouth  to  open  very  wide,  but  the  teeth  serve  only  for  seizing  and 
holding  the  prey.  In  the  venomous  snakes  in  the  upper  jaw  are  found 
the  "poison  fangs"  which  have  a  channel  leading  to  the  poison  sac. 
The  chelonidcB  or  turtles  have  a  horn-like  covering  for  the  border  of  the 
jaw. 


Fig.  70. — Specialized  conical  teeth  in  the  higher  order  of  fishes. 


The  birds,  of  course,  have  no  teeth,  the  beak  being  a  horny  sheathing 
of  the  ends  of  the  jaw-bones.  In  some  the  edge  is  serrated.  In  no  other 
class  is  found  a  greater  variation  in  the  food-preparing  apparatus,  or 
greater  adaption  to  the  food  supply.  The  beak  serves  largely  to 
obtain  the  food.  In  the  grain-eating  birds  the  gizzard  performs 
mastication.  Ducks  have  soft-edged  beaks  for  sifting  the  food  out  of 
the  mud.  The  skulls  of  the  hawk,  heron,  English  sparrow,  crow,  and 
toucan  shown  give  an  idea  of  this  variation.  The  crow  subs'ists  largely 
on  grain,  and  very  often  takes  grain  such  as  corn  out  of  the  husk.  It 
has  rather  a  strong  beak  suited  for  this  purpose  (Fig.  71). 

The  skull  of  the  blue  heron  is  also  shown.  These  are  aquatic  birds, 
and  their  food  comes  from  the  bottom  of  the  water,  or  in  fact,  down  in 
the  mud  where  they  go  after  little  frogs  and  little  fish,  and  various 
other  inhabitants  of  the  water.  Also  is  shown  passer  domesticus  or 
English  sparrow,  which  subsists  on  very  much  the  same  type  of  food 
as  the  crow,  only  it  is  a  little  more  omnivorous,  and  the  beak  is  very 
much  the  same.  We  also  have  the  skull  of  a  South  American  bird,  the 
toucan,  which  is  a  fruit-eating  bird.    The  serrations  on  the  beak,  which 


208 


THE   TEETH   AS  A   MASTICATING  MACHINE 


are  useful  in  cutting  through  the  skin  of  fruit  and  in  sifting  out  the 
stones,  will  be  noted  as  a  rather  interesting  adaptation  to  the  needs  of 
this  bird.  Lastly,  we  see  the  skull  of  the  hawk,  one  of  the  carnivorous 
birds.     The  beak  of  the  hawk  is   very  strong,  and  is  used  for  the 


^^« 

9 

C^**- 

1 

Fig.  71. — -Beaks  of  birds  showing  functional  modifications. 

purpose  of  killing  the  prey :  smaller  birds,  and  mammals,  in  the  case  of 
large  hawks,  and  insects  and  food  of  that  sort  in  case  of  smaller  hawks. 
There  is  very  much  the  same  type  of  masticating  apparatus,  if  it  may 
be  so  called,  in  the  turtle.  Fig.  72  shows  the  skull  of  a  large  greeji  turtle, 
the  hawk-bill  turtle,  whose  bill  is  covered  with  a  very  hard,  dense  mem- 


FiG.  72.— Skull  of  a  ix.rccu  turtle. 


brane,  which  is  very  honi-hkc  in  cjuality,  and  is  very  much  like  the 
beak  of  birds,  the  jjurpose  of  it  being  j)urely  to  crush  the  food,  and  to 
cut  off  a  definitely  si/,ed  amount  of  food  in  order  that  it  may  be  swal- 
lowed.    Of  cours(;  it  it  not  possible  for  this  animal  to  chew  its  food. 


EVOLUTION   OF   TOOTH  FORMS  209 

The  first  type  of  tooth  that  is  of  very  great  interest  other  than  merely 
as  a  fang,  or  something  of  that  sort,  is  the  molar  of  the  ungulates 
which  are  herbivorous  and  granivoroiis  animals  (Fig.  73).  Herbivo- 
rous animals  live  on  grain  and  on  vegetable  fiber,  both  of  which 
require  considerable  trituration  in  order  to  be  successfully  acted  upon 
by  the  digestive  juices,  solvents  and  ferments  farther  down  in  the 
digestive  tract.  For  example,  corn  and  other  grains  will  pass  down  the 
alimentary  tract  of  any  of  these  animals  entirely  untouched  unless  the 
outer  membrane  is  broken,  therefore  in  order  to  be  successfully 
digested  they  ha\'e  to  be  well  triturated. 

The  series  of  molar  teeth  of  the  horse  is  a  real  grinding  machine. 
The  surface  is  raised  into  elevations  alternating  with  depressions.  The 
elevations  are  the  enamel,  the  depressions  between,  the  cementum. 


Fig.  73. — Skull  of  a  sheep. 

The  cementum  is  very  much  softer,  and  as  the  tooth  wears  down  the 
enamel  which  is  harder  and  more  resistant  than  the  cementum  wears 
much  less  rapidly,  so  that  the  surface  is  continually  kept  rough  for 
grinding  purposes. 

This  animal  has  a  great  latitude  in  the  side-to-side  movement  of 
the  jaw;  or,  to  speak  more  technically,  the  lateral  excursion  of  the 
mandible  of  herbivorous  animals  is  very  marked.  The  jaw  does  not 
move  much  backward  and  forward;  in  fact,  it  hardly  moves  in  these 
directions  at  all,  but  it  moves  from  side  to  side.  The  result  is  that 
these  serrations  run  from  front  to  back.  This  is  exactly  the  reverse  of 
the  form  of  the  molars  found  in  the  rodents,  in  which  a  backward-and- 
forward  movement  of  the  mandible  is  responsible  for  the  grinding, 
necessitating  a  different  arrangement  of  the  occlusal  surface  of  the 
teeth. 
14 


210  THE   TEETH  AS  A   MASTICATING  MACHINE 

John  Ryder,  many  years  ago,  pointed  out  the  fact  that  from  an  exami- 
nation of  the  surfaces  of  the  molar  teeth  of  any  animal,  extinct  or 
living,  he  could  without  reference  to  the  skull  indicate  the  way  in  which 
the  mandible  was  accustomed  to  move. 

The  front  of  the  mouth  of  the  horse  is  provided  with  incisor  teeth 
which  bite  and  pinch  off  the  grass  and  other  foods  which  the  animal 
secures.  The  canine  is  quite  rudimentary,  and  usually  absent  in 
the  mare. 

Cows  have  incisors  only  in  the  lower  jaw,  and  the  biting  is  done 
between  the  upper  lip  and  the  lower  teeth. 


1 

HH^I 

KI^I 

Fig.  74. — Carnivorous  and  herbivorous  skulls. 

Now  passing  over  one  or  two  important  orders  as  not  being  especiall}' 
interesting,  next  comes  a  very  large  family  in  the  animal  kingdom, 
the  carnivorous  animals,  which  differ  from  the  class  just  described 
in  the  character  of  their  teeth  and  also  in  the  manner  of  the  move- 
ment of  the  mandible.  In  studying  these  dentures  three  funda- 
mental elements  and  their  relationship  myst  be  constantly  borne 
in  mind;  the  food  supply,  the  teeth,  and  the  manner  in  which  the 
mandible  is  capable  of  moving. 

For  a  comjjarison  of  dentures  the  skulls  of  a  large  western  cat  and  of 
an  ordinar.N'  buck  sheep  arc  pictured  together  (Fig.  74).  A  vast  differ- 
ence in  the  grinding  teeth,  as  shown  in  their  respective  mandibles,  is 


EVOLUTION  OF   TOOTH  FORMS  211 

noted.  In  one  the  teeth  are  narrow,  in  the  other  the  teeth  are  wide. 
Viewed  from  the  side  it  is  seen  that  the  carnivorous  molars  have 
sharp  edges  and  are  rather  more  Hke  knives  than  the  grinders 
of  the  herbivorous .  series.  In  one  there  are  very  pronounced 
canines. 

There  is  a  very  marked  difference  in  the  temporomandibular  articu- 
lation of  these  two  animals.  In  the  case  of  the  herbivorous  animals 
there  are  broad,  flat  glenoid  fossae  to  render  possible  the  large  range 
of  lateral  excursion  of  the  mandible.  On  the  other  hand,  the  carnivor- 
ous animals  have  no  lateral  excursion.  The  condyles  fit  into  the  fossse 
so  tightly  as  to  make  almost  a  hinge  joint;  and  in  some  instances 
the  distal  part  of  the  eminentia  articularis  so  far  overhangs  its  glenoid 
fossa  that  it  cannot  be  seen.  It  is  only  with  great  difficulty  that  the 
condyles  can  be  gotten  out  of  these  fossse;  indeed  in  some  instances 
they  cannot  be  gotten  out  without  breaking  the  skull. 


Fig.  75. — Skull  of  a  tiger. 

In  the  skull  of  an  Indian  tiger,  it  may  be  noticed  that  the  molar  teeth 
are  of  the  type  described  (Fig.  75).  They  are  very  sharp,  and  there 
are  tubercles  on  each  side  just  before  the  cingulum  is  reached,  and  in 
the  closure  of  the  mouth  the  teeth  pass  by  each  other  very  much  like 
the  blades  of  a  pair  of  shears.  Besides  the  articulation  of  the  mandible 
which  serves  to  keep  it  in  line,  the  upper  canines  fit  into  the  spaces 
back  of  the  lower  canines  and,  locking  the  occlusion  like  guide-pins, 
prevent  lateral  movement. 

The  carnivora  have  greater  crushing  power  in  their  jaws  in  com- 
parison to  their  size  than  any  other  animals.  Thi^  is  partly  due  to 
the  tremendous  temporal  muscles  which  are  attached  to  the  broad 
temporal  ridges. 

In  the  skull  of  a  black  hear  is  observed  almost  the  same  type  of  den- 
tition as  that  of  the  cats,  only  the  canine  teeth  are  a  little  less  powerful, 


212 


THE   TEETH  AS  A   MASTICATING  MACHINE 


and   the  carnassial   teeth  at  the  rear  are  not  so  strongly  marked 
(Fig.  76). 

A  typical  carnivorous  dentition  is  found  in  the  canincp  or  dog  family, 
and  in  a  skull  of  the  canis  latrans  illustrated  are  shown  the  several  types 


Fig.  76. — Skull  of  a  black  bear. 


Fig.  77. — Kkull  of  u  coyote. 


of  teeth  definitely  marked;  the  incisors,  three  on  each  side,  the  canines, 
the  ])romolars  and  the  molars  (Fig.  77).  In  the  upper  jaw  there  are  four 
premolars  and  two  molars,  whereas  in  the  lower  jaw  there  are  three 
molars  and  four  j)remolars.     The  fourth  uj)per  i)remolar  and  the  first 


EVOLUTION  OF  TOOTH  FORMS  213 

lower  molar  are  known  as  the  earnassial  teeth  and  they  are  the  chief 
cutting  teeth  of  these  animals. 

In  the  wolf  and  the  American  fox  the  dentition  is  precisely  the  same. 
In  some  of  the  smaller  carnivorous  animals,  the  badger,  the  otter,  and 
the  raccoon,  the  dentition  is  very  much  the  same. 

The  next  family  is  the  rodents,  who  have  a  highly  developed  type  of 
incisor.  Thus  far  attention  has  been  given  chiefly  to  the  molar  teeth. 
In  the  rodents  the  incisor  teeth  are  of  the  greater  importance.  In  the 
skull  of  the  beaver  the  upper  incisor  tooth  has  a  chisel-like  beveled 
edge  (Fig.  78).  It  has  enamel  only  upon  its  labial  surface,  which  is 
supported  by  the  dentin.  There  is  no  enamel  on  the  back  of  the 
tooth.  As  the  dentin  wears  away  the  enamel  is  left  standing  and  chips 
away  and  thus  always  preserves  a  sharp  edge.  It  is  really  a  self-sharpen- 
ing tool.     It  has  a  persistent  pulp  and  grows  out  as  it  is  worn  off. 


^^^^^^ 

3 

r 
1 

^pf^.  .•  ^:^^^^^ 

fe 

^ 

^_T| 

E:\  T^->>,«rf(^^i1 

■ 

^ 

^^TgMl 

^^^K.  '                                 ':  :^^^ii^By 

K 

^^^^^^H 

■ 

■ 

^^^2^1 

Fig.  7S. — Skulls  of  rodents. 

The  rodents  have  practically  no  lateral  motion  to  the  mandible,  but 
great  backward-and-forward  movement.  Their  molars  are  ridged,  but 
the  ridges  run  transversely,  so  that  in  the  backward-and-forward 
movement  of  the  mandible  they  can  do  the  sarne  kind  of  grinding  as 
the  herbivorous  animals  do  in  the  lateral  movement  (Fig.  79). 

Approaching  nearer  to  man  in  the  scale  of  animal  life,  as  for  example 
in  the  apes,  dentures  are  found  which  are  approximately  like  the 
hiunan  one.  Thus  in  the  new  world  monkeys  (Fig.  80)  almost  exactly 
the  same  type  of  denture  is  observed  as  that  of  man,  except  that 
there  are  three  premolars  instead  of  two.  There  are  two  incisors, 
a  canine,  three  premolars  and  three  molars  on  each  side. 

The  old  world  monkey  is  the  first  animal  representing  exactly  the 
dental  formula  of  man  (Fig.  81).  The  three  molars,  the  two  pre- 
molars, the  canines  and  the  incisors  are  the  same.  There  is,  however^ 
a  space  between  the  upper  lateral  incisor  and  the  canine  which  is  to 


214 


THE   TEETH  AS  A   MASTICATING  MACHINE 


admit  the  lower  canine.    These  animals  are  largely  frugivorous,  and 
their  teeth  are  suitable  for  this  diet. 


Fig.  79. — Skulls  of  rodents  showing  transverse  ridges  in  molar  teeth. 


Fig.  80. — Skull  of  a  new  world  monkey. 


The  baboon  has  very  long  teeth  and  exactly  the  same  dentition  as 
has  been  seen  before,  that  is,  it  has  the  same  formula.    The  molar 


THE   TEETH  OF  THE  ANTHROPOID  APES  215 

teeth  are  very  miicli  the  same  in  general  form  as  the  human  molars. 
The  chimpanzee  has  a  deciduous  denture  which  is  even  more  Hke  that 


Fig.  81. — Skull  of  an  old  world  monkey. 


Fig   82. — Skull  of  a  chimpanzee  showing  deciduous  denture. 


216 


THE   TEETH  AS  A   MASTICATING  MACHINE 


of  man  (Fig.  82).  The  gorilla  has  a  very  powerful  mandible  and  the 
canines  are  very  strongly  developed. 

It  is  not  such  a  very  long  step  from  the  dentures  of  the  anthropoid 
apes  to  one  of  the  lower  types  of  human  denture  (Fig.  83).  The 
skull  sho-UTi  is  not  of  the  lowest  aboriginal  type,  but  the  highly  devel- 
oped jaws  will  be.  noted  while  the  skull  case  which  contains  the  brain 
is  not  highly  developed. 

Secondary  Functions  of  the  Teeth. — It  might  be  interesting  to  dwell 
for  a  moment  upon  certain  secondary  functions  developed  in  connec- 


^H 

■H- 

^ 

^ 

^^d 

n 

ir^. 

'i^^^  ''^'  ii^i^^^^^^H 

^^E 

A 

Rw^Si^^^v^ih^^^^^lw^^^^^H 

PHM 

P^H 

i 

^  1 

|P; 

■ '  IB 

r^H 

1 

\n 

P'       .: 

wm 

I  '^ 

w 

^ 

Hr  ,^ 

w      . 

M 

m 

gfc^ 

■HlMhr^ 

fc~    i 

w 

■ 

^^HH^j^^^' 

H 

^^R^^F^^^ 

^^ 

1 

1 

Fig.  83. — Architectural  construction  of  skeletal  portion  of  masticating  apparatus: 
the  fixed  base,  and  moveable  arm.  Columns,  arches,  and  buttresses  of  the  fixed  base; 
frontonasal  column,  A  B;  zygomatic  column,  C  M  D;  pterygoid  column  (only  partly 
visible),  supra-orbital  arch,  B  F  D;  infra-orbital  arch,  B  I  D;  upper  nasal  half-arch, 
B  G;  palatal  arch  (not  shown) ;  lower  nasal  arch,  A  H;  large  molar  arch,  A  C;  molar 
buttresses  (descending  from  M) ;  pterygoid  arches  (not  shown) .  Columns  and  arches 
of  the  moveable  arm;  mental  column,  N  K;  coronoid  column,  P  Q  0;  and  condyloid 
column,  /  L;  external  oblique  column,  Q  N.  (From  a  photograph  of  specimen  No. 
4237,  Wistar  Institute  of  Anatomy.)     (Turner.) 


tion  with  the  teeth.    Since  secondary  functions  are  performed  by  the 
teeth  of  man,  those  we  find  in  the  animals  may  be  briefly  viewed. 

They  are  used  as  weapons  of  offence,  as  in  the  poison  fangs  of 
the  snake,  which  is  a  very  well-known  example.  The  hypodermic 
needle  really  had  its  origin  in  the  poison  fang  of  the  viperine  snakes, 
a  tooth  with  a  tube  extending  through  its  center  and  leading  to  the 
poison  sac.  Upon  the  contraction  of  the  digastric  muscle  and  opening 
of  the  mouth  the  fang  is  erected,  and  when  it  is  driven  into  the  prey 
the  sac  at  its  base  is  compressed  and  the  poison  injected.        , 


THE  HUMAN  DENTAL  MECHANISM 


217 


The  swnrd-fi.sh  has  a  very  dangerous  projection  which  it  uses  to  open 
the  al)domen  of  fish  from  beneatli  and  thus  kills  them.  The  use  of 
teeth  as  weapons  in  warfare  is  well  known,  as  in  the  rhinoceros  and 
even  our  domestic  animal,  the  Jiorse.  The  teeth  are  also  used  for  pur- 
poses of  transportation  and  locomotion.  The  elepha?it  uses  his  tusks, 
which  are  very  highly  developed  upi)er  incisors,  to  uproot  trees,  and 
dig  up  tuberous  roots.  He  is  trained  in  India  to  use  them  for  the 
purpose  of  transporting  lumber,  etc.  The  walrus  uses  his  upper 
canine  teeth  to  pull  himself  up  on  the  ice,  and  also  for  digging  in  the 
mud  and  uncovering  small  fish,  shell  fish,  etc.,  which  he  consumes. 
One  of  the  most  interesting  of  the  secondary  uses  of  the  teeth  is  found 
in  one  of  the  lemurs.  The  flying  lemur  (galeopithecus  volans)  has 
curious  incisor  teeth,  the  lingual  side  of  which  is  very  much  like  the 
teeth  of  a  comb,  and  this  the  animal  uses  to  comb  its  fur. 


Fig.  84. — Upper  and  lower  teeth  in  occlusion.     (From  photograph  of  specimen  in 
the  Wistar  Institute  of  Anatomy.) 

The  Human  Dental  Mechanism. — The  human  dental  mechanism  prima- 
rily has  to  do  with  the  preparation  of  the  food  for  subsequent  stages 
in  its  digestion,  and  it  is  a  very  interesting  apparatus  viewed  as  a 
machine,  created  for  this  purpose.  To  better  understand  it,  for  pur- 
poses of  study,  it  may  be  resolved  into  its  various  elements.  In  the 
first  place  it  consists  of  a  fixed  base  and  a  movable  arm  (Fig.  84) .  The 
fixed  base  is  the  upper  jaw,  and  the  movable  arm  is  the  lower  jaw.  It 
has  been  likened  to  a  hammer  and  anvil  turned  upside  down;  but  the 
metaphor  of  the  fixed  base  and  movable  arm  is  a  little  more  expressive. 
These  two  elements  are  equipped  with  teeth,  the  armament  of  the  appa- 
ratus.   Between  these  two  elements  extend  the  muscles  which  elevate 


218  THE   TEETH  AS  A   MASTICATING  MACHINE 

the  mandible  and  constitute  the  motive  power  of  the  machine.  Ordina- 
rily they  are  spoken  of  as  the  muscles  of  mastication;  the  masseter,i\\e 
temporal  and  the  two  pterygoids;  and  then  at  the  front  end  of  the  man- 
dible are  muscles  attached  to  the  genial  tubercles  to  assist  in  lowering 
the  mandible,  the  digastric  and  the  geniohycrid,  and  the  muscle  which 
forms  the  floor  of  the  mouth,  the  mylohyoid.  This  whole  apparatus  is 
found  in  the  cavity  of  the  mouth.  The  cheeks  and  the  lips  on  the  out- 
side serve  as  the  outer  walls  of  the  cavity  which  contains  the  food  while 
it  is  being  masticated.  The  tongue  on  the  inside  is  actively  engaged 
in  keeping  the  food  between  the  crushing  surfaces,  and  assists  the 
cheeks  and  lips  in  that  way.  The  last  element  of  the  apparatus 
is  the  salivary  glands,  the  secretions  of  which  have  both  a  mechanical 
and  physiological  function.  They  lubricate  the  machine,  soften  and 
dissolve  the  food,  and  agglutinate  it  for  deglutition,  besides  performing 
a  digesti\'e  function  in  connection  with  the  food. 

The  several  portions  of  the  apparatus  will  be  taken  up  and  discussed 
a  little  more  in  detail.  The  fixed  base,  which  is  the  two  maxillae 
united  in  the  median  line,  is  supported  upon  the  skull  by  a  number  of 
very  strong  colmims  or  supports.  It  may  be  better  seen  if  this  base  is 
considered  as  if  it  were  upside  down.  There  are  several  of  these  bony 
columns,  one  going  inside  the  orbit  and  reaching  the  skull  in  the  median 
line.  {A  B,  Fig.  83.)  There  is  another  one  from  above  the  first  or 
second  molar  going  right  up  through  the  malar  bones  and  the  outer 
border  of  the  eye  {C  M  D).  When  the  skull  is  viewed  from  below 
still  another  column  is  seen.  This  is  the  pterygoid,  which  supports 
the  distal  end  of  the  dental  arch. 

The  Mandible. — The  lower  jaw  is  the  movable  element,  the  movable 
arm.  It  has  the  general  shape  of  the  letter  "U"  and  the  ends  of  the 
"U'^  are  bent  upward  at  the  end  and  terminate  in  the  condyloid  pro- 
cesses. There  are  several  layers  of  soft  tissues  intervening  at  the 
joint  which  are  placed  there  to  lessen  the  shock  of  mastication,  and 
permit  the  movement  of  the  joint.  Between  this  point  and  the  anterior 
end  the  muscles  of  mastication  are  attached.  They  move  the  man- 
dible as  a  lever,  one  end  of  which  is  fixed  and  constitutes  the  fulcrum. 
Ilie  muscles  are  attached  between  this  end  and  what  is  the  weight  end 
of  tlie  lever,  the  forward  portion  which  does  the  work.  Thus  it  is  a 
lever  of  the  third  class.  The  fulcrum  exists  in  the  tempomandibular 
joint  which  is  interesting  from  a  mechanical  standpoint  because  it 
has  so  much  to  do  with  the  way  in  which  the  mandible  can  move. 
The  form  of  the  glenoid  fossa  is  a  large  factor  in  this.  The  jaw  cannot 
move  backward  but  it  can  move  forward  and  downward  until  it  is 
somewhere  near  the  summit  of  the  eminentia  articularis.  It  can  also 
rotate  about  a  horizontal  axis,  passing  approximately  through  the 
condyles.  In  considering  the  manner  of  movement  of  the  mandible 
it  will  be  seen  how  the  joint  renflers  these  movements  possible.  Its 
movement  is,  of  course,  limited  l)y  ligaments.  There  is  the  capsvlar 
ligament  which  is  thickened  at  the  back  into  a  very  thick  band,  which 


THE  MOVEMENT  OF   THE  MANDIBLE  219 

prevents  the  jaw  from  going  too  far  forward.  The  external  and  inter- 
nal lateral  Hgaments  are  really  nothing  more  or  less  than  still  greater 
thickenings  of  the  capsular  ligament  itself  on  the  outside  and  inside 
of  the  joint  respectively  which  prevent  the  motion  of  the  jaw  laterally. 

The  other  ligaments,  the  stylomandibular  and  s'phenomandihnlar, 
which  are  largely  thickenings  of  the  cervical  fascia,  do  not  have  very 
much  to  do  with  the  way  with  which  the  mandible  can  move. 

Of  the  muscular  apparatus  it  is  quite  unnecessary  to  speak  exten- 
sively. The  masseter  is  the  muscle  most  concerned  in  the  elevation  of 
the  jaw,  and  the  temporal  and  internal  yterygoid  aid  in  this  movement. 
The  function  of  the  external  pterygoid  must  be  kept  in  mind  in  that 
it  is  attached  to  the  interarticidar  fibrocartilage  as  well  as  to  the  neck 
of  the  condyle,  and  serves  to  pull  them  both  forward  in  the  forward 
movement  of  the  jaw. 

The  direction  in  which  the  mandible  can  move  may  now  be  noted. 
First  the  simplest  form  of  movement  may  be  taken  up,  starting  from 
that  position  of  the  mandible  in  which  the  teeth  are  in  occlusion. 
This  is  the  point  toward  which  all  the  movements  of  mastication 
ultimately  tend.  With  the  teeth  in  occlusion,  what  happens  when 
the  mandible  is  depressed?  The  external  yterygoid  muscle  on  each 
side  contracts  and  pulls  its  condyle  downward  and  forward.  The 
condyles  slide  down  the  walls  of  the  glenoid  fossae.  The  digastric 
and  geniohyoid  muscles  attached  to  the  genial  tubercles  contract 
and  pull  down  the  front  end  of  the  mandible.  The  effect  of  these 
contractions  is  to  carry  the  front  end  of  the  mandible  down  and 
the  distal  ends  forward.  The  mandible  does  not  rotate  about  a  fixed 
axis,  but  the  condyles  are  being  carried  forward  at  the  same  time 
that  rotation  is  taking  place.  In  other  words,  there  is  a  combination 
of  sliding  and  of  rotation.  When  the  mouth  opens  the  condyles 
slide  forward  and  downward,  and  the  front  end  of  the  mandible  is 
depressed.  The  mouth  could  not  be  opened  if  the  condyles  remained 
in  the  back  part  of  the  fossae. 

There  is  then  a  combination  of  rotation  about  a  horizontal  axis 
passing  through  the  condyles  and  a  sliding  motion.  It  so  happens 
that  the  front  teeth  describe  what  is  approximately  the  arc  of  a  circle 
while  they  are  sliding  and  rotating;  but  the  center  of  that  circle  is 
not  in  the  condyles,  but  considerably  back  of  them. 

When  the  mandible  is  brought  up  again  to  the  occlusal  position 
the  reverse  of  this  takes  place,  but  Tomes  and  Dolamore  have  found 
out  by  tracing  a  large  number  of  jaws  that  the  path  of  closing  is 
always  a  little  bit  in  front  of  that  of  opening.  Direct  opening  and 
closing  is  a  type  of  movement  seen  in  the  carnivora.  The  condyles 
do  not  slide  forward.  In  the  herbivorous  animal  there  is  a  lateral 
movement.  In  that  lateral  movement  one  condyle  remains  in  the 
fossa  and  the  other  one  slides  dowaiward,  forward,  and  inward.  This 
type  of  movement  is  also  noted  in  the  human  jaw.  One  of  the 
condyles  remains   in   its   fossa,  the  other    one  being   pulled  down- 


220  THE   TEETH  AS  A   MASTICATING  MACHINE 

ward  and  forward  by  the  contraction  of  the  external  'pterygoid  muscle 
of  the  side.  Of  course  that  means  that  the  two  pterygoid  muscles  are 
capable  of  independent  contraction.  The  mandible  rotates  approxi- 
mately about  the  center  of  the  stationary  condyle.  The  same  occurs 
when  the  jaw  moves  to  the  other  side,  as  it  simply  reverses  the  mov- 
ing and  the  stationary  condyles. 

If  both  external  -pterygoids  contract,  the  jaw  is  carried  forward  or 
protruded.  If  they  contract  independent  of  the  muscles  attached  to 
the  front  end  of  the  mandible  there  is  a  protrusion  of  the  mandible. 
That  is  a  type  of  movement  characteristic  to  the  rodents  or  the 
gnawing  animals.  There  is  then  in  the  human  jaw  the  possibility  of 
these  three  distinct  types  of  movements. 

Now  that  the  fixed  base  and  the  movable  arm  and  the  motive  power 
of  the  apparatus,  and  the  manner  in  which  the  mandible,  or  the  movable 
element  may  be  actuated  have  been  described,  the  teeth  will  be  dis- 
cussed from  the  standpoint  of  their  form  and  arrangement  as  suitable 
to  the  working  of  the  machine. 

A  Study  of  the  Human  Denture. — In  the  first  place  the  forms  of 
human  teeth  are  modified  or  fused  cones,  as  are  all  animal  teeth  (Fig. 
84).  The  incisors  are  cones  with  a  flattened  end  and  may  be  likened 
to  the  form  of  a  chisel.  This  type  of  a  tooth  is  especially  well  devel- 
oped in  the  rodents.  The  canine  tooth  is  more  nearly  a  cone  of  simple 
form  than  any  other,  although  not  perfectly  circular  in  cross-section. 
It  is  similar  in  general  form  to  the  canine  teeth  in  the  carnivora,  more 
like  them  perhaps  in  a  general  way  than  that  of  any  other  animal 
types,  the  canine  in  the  herbivora  being  either  lacking  or  very 
rudimentary  in  character. 

The  bicuspids  (the  term  being  derived,  of  course,  from  their  two- 
cusped  or  two-coned  character)  are,  as  has  been  indicated,  merely  two 
cones  fused  together. 

The  molars,  on  the  other  hand,  have  a  number  of  cones  fused  together, 
each  cone  represented  by  a  cusp;  in  case  of  the  lower  first  molar  nor- 
mally five  cusps,  and  the  others  only  three  or  four. 

The  teeth  are  arranged  in  two  arched  series,  consisting  normally 
of  thirty-two  teeth,  sixteen  in  each  series  (Figs.  85  and  86).  The 
actual  outline  of  this  arch  varies  with  individuals,  but  within  certain 
bounds  this  variation  in  form  has  no  relationship  whatever  to  its 
functional  efficiency. 

The  upper  arch  is  larger  and  overhangs  the  lower.  The  upper  teeth 
constitute  the  fixed  base  in  relation  with  which  the  lower  teeth  move, 
therefore  the  upper  arch  would  necessarily  cover  a  larger  area  in 
order  to  permit  the  movement  of  the  lower  over  its  surface. 

On  the  inside  of  the  teeth  is  the  tongue,  on  the  outside  the  lips  and 
cheeks.  The  overhang  of  the  molar  and  bicuspid  series  in  the  rear, 
and  of  the  incisors  in  the  front  of  the  month  not  only  serve  the  useful 
purpose  of  providing  a  larger  area  over  which  tlie  lower  jaw  may  move, 
but  it  serves  to  hold  the  lips  and  teeth  out  of  the  way  and  prevents 


THE  HUMAN  DENTURE  221 

their  being  caught  between  the  crushing  surfaces.  On  the  inside 
the  fact  that  the  lower  teeth  overhip  and  pass  up  the  inner  sides 
of  the  upper  teeth  serves  a  similar  purpose  of  keeping  the  tongue 
out  of  the  way. 


Fig.  85. — Occlusal  surfaces  of  the  upper  teeth. 

One  may  realize  how  useful  this  provision  is  if  one  observes  a  set 
of  artificial  teeth  in  which  this  overhang  is  not  properly  provided,  when 
the  wearer  will  frequently  complain  that  he  bites  his  cheeks.  Instances 
of  the  same  difficulty  are  seen  in  mouths  with  full  sets  of  natural  teeth, 
the  cusps  of  which  have  worn  do\\ai,  and  in  which  the  lower  jaw  has 
moved  forward  to  what  is  designated  an  edge-to-edge  bite.     There  is 


Fig.  86. — Occlusal  surfaces  of  the  lower  teeth, 

no  doubt  of  the  authenticity  of  the  reported  case  of  a  well-known  man 
who  lost  his  life  tlirough  cancer  originating  in  the  irritation  of  the 
cheek  from  biting  it  when  the  cusps  of  his  teeth  had  worn  off  until  he 
had  an  edge-to-edge  bite. 


222  THE  TEETH  AS  A   MASTICATING  MACHINE 

The  series  of  teeth  normally  present  an  unbroken  surface  from  one 
end  around  to  the  other;  that  is,  there  are  no  spaces  between  them,  as 
in  some  of  the  animals,  particularly  the  carnivorous  animals.  Man  is 
the  only  animal  not  having  diastemata,  or  spaces  between  his  teeth. 
This  is  provided  for  by  the  bell-like  shape  of  the  crowns  of  the  teeth 
which  do  not  touch  at  their  necks  but  at  the  point  of  interproximal 
contact.  This  contact  serves  to  protect  the  gum  tissue  below  from 
injury  from  the  food  such  as  meat  and  vegetable  fibers.  If  one  has 
experienced  what  it  is  in  one's'  own  denture  to  have  a  flat  filling,  or 
none  at  all,  in  consequence  of  which  food  packs  in  and  produces  the 
long  train  of  uncomfortable  results,  one  will  understand  how  wise  is 
this  provision  of  nature. 

Occlusion. — The  occlusion  of  the  teeth,  to  attempt  a  very  offhand 
definition,  is  the  relationship  of  their  morsal  surfaces  when  the  man- 
dible is  in  the  position  of  the  resting  bite  (Fig.  87).  The  phrase  is  used 
to  indicate  the  relationship  of  the  upper  and  lower  teeth  when  in  such 
contact  that  there  is  a  definite  fitting  together  of  their  surfaces.  In  the 
occlusal  position  the  condyles  of  the  mandible  are  in  the  most  distal 
part  of  the  glenoid  fossse.  When  the  teeth  are  in  occlusion  the  muscles 
extending  between  the  jaws  are  either  in  a  state  of  tonic  contraction, 
simply  holding  the  jaw  up,  or  they  may  be  actively  contracted,  that 
is,  pressing  the  lower  teeth  firmly  upon  the  upper  ones.  This  is  a 
rather  fundamental  position  of  the  jaw.  It  is  a  position  of  equilibrium. 
It  is  to  this  position  and  from  this  position  that  all  the  various  move- 
ments incident  to  mastication  take  place.  In  the  crushing  of  the  food 
the  jaw  tends  to  return  from  its  various  excursions  to  the  occlusal 
position. 

The  occlusion  of  the  teeth  then  means  the  definite  relationship 
existing  between  the  occlusal  or  morsal  surfaces  of  the  teeth.  This 
must  be  carefully  considered,  for  in  order  to  understand  the  machine 
in  motion  it  must  first  be  studied  in  repose.  Perhaps  simplicity  will 
be  consulted  by  dividing  the  description  of  the  occlusion  into  that  of 
the  incisor  teeth,  and  that  of  the  molar  and  bicuspid  teeth. 

As  to  the  incisors,  which  are  flat  and  wedge-shaped,  the  upper  over- 
hang the  lower,  the  incisal  edges  of  the  lower  resting  normally  in  con- 
tact with  the  lingual  or  inside  surfaces  of  the  upper  teeth.  This  nor- 
mal overhang  or  overbite  is  approximately  one-third  of  the  length  of 
the  lower  teeth,  although  of  course  it  is  subject  to  slight  variation.  The 
canine  tooth  is  really  intermediate  in  the  character  of  its  occlusion 
between  the  incisor  and  the  bicuspid  series.  It  partakes  of  the  char- 
acteristics of  the  incisors  in  that  it  overhangs  the  lower  teeth,  but  it 
is  like  the  bicuspids  in  having  a  sharp  cusp  exactly  like  the  buccal  cusps 
of  the  bicuspids. 

When  the  teeth  have  worn  down  either  from  having  had  a  very  small 
overbite  and  short  cusps  f)riginally,  or  from  the  use  of  coarse  food,  so 
that  there  is  an  edge-to-edge  bite,  the  machine  is  by  no  means  as  eft'ec- 
tive  as  in  the  arrangment  referred  to  as  normal.    In  the  latter  case  the 


A  STUDY  OF  OCCLUSION  223 

food  is  simply  pinched  off  and  not  sheared  off  as  when  the  upper  incisors 
overhang. 

In  the  study  of  the  occhision  of  the  molar  and  bicuspid  series  of  teeth 
the  occlusal  surfaces  should  be  first  considered  (Figs.  85  and  86). 
It  will  be  noted  that  they  exhibit  two  rows  of  cones  with  depres- 
sions or  fossae  intervening  between  them.  On  this  surface  of  the 
bicuspids  there  is  a  cone  on  the  iimer  and  outer  side.  In  studying 
the  molars  there  w411  be  found  two  cones  on  the  inner  and  outer 
sides,  except  on  the  third  molar  where  the  distolingual  cusp  may  be 
lacking. 

There  are  then  a  row  of  inner  and  a  row  of  outer  cones,  with  fossae 
or  little  pits  intervening  between  them.  There  are  transverse  ridges 
dividing  one  fossa  from  another.  The  same  thing  is  true  of  the 
occlusal  surfaces  of  the  lower  series  of  teeth.  They  have  a  definite 
arrangement,  a  row  of  outer  and  a  row  of  inner  cusps  w4th  fossae 
between.  However,  there  is  a  difference  in  the  shape  in  these  two  rows 
of  cusps.  The  inner  ones  are  rounded  in  the  upper  series  of  teeth 
and  are  considerably  larger  than  those  in  the  outer  row.  Speaking 
technically,  the  lingual  are  larger  than  the  buccal  cusps,  which  are 
sharp  and  thin,  while  the  reverse  of  this  is  true  of  the  lower  teeth.  The 
buccal  cusps,  or  outer  cones,  are  the  large  round  ones;  the  inner  cusps 
are  sharp  and  thin.  The  rounded  cusps  in  both  series  are  really  the 
functionating  cusps.  They  are  the  ones  which  are  received  into  the 
fossae  when  the  teeth  are  in  the  occlusal  position.  If  an  upper  set  of 
teeth  is  superposed  upon  a  lower,  it  will  be  found  that  the  lower  buccal 
cusps  occupy  the  fossae  of  the  upper  series  and  the  rounded  lingual 
cusps  of  the  upper  fit  into  the  fossae  in  the  lower  set  of  teeth. 

It  is  not  enough  in  the  normal  arrangement  that  any  cusp  should 
fit  into  any  fossa.  In  normal  occlusion  there  is  a  definite  fossa  for 
each  cusp  to  occupy  (Fig.  87).  Orthodontists  have  accepted  a  simple 
method  of  determining  when  a  denture  is  in  normal  occlusion. 
They  look  to  see  if  the  mesiobuccal  cusp  of  the  first  upper  molar 
occupies  the  buccal  groove  of  the  first  lower  molar  and  if  so  and  the  other 
cusps  fit  into  their  fossa^,  and  so  on,  then  the  occlusion  is  correct.  If 
this  cusp  is  in  front  of  or  back  of  the  buccal  groove  then  it  would  not 
be  normal  occlusion;  there  might  be  an  interdigitation  of  the  cusps 
but  it  would  not  be  perfectly  normal,  unless  each  cusp  occupied  its 
own  particular  fossa. 

In  an  inner  view  of  the  denture  (Fig.  88),  the  overlapping  of  the  sharp 
and  thin  inner  cusps  of  the  lower  teeth  wdll  be  noted,  each  fitting  into 
a  groove  or  space  on  the  lingual  surfaces  of  the  upper  teeth.  This  inter- 
digitation has  also  another  rather  interesting  advantage,  and  this  is 
that  each  tooth  of  both  series,  with  two  exceptions,  is  opposed  by  two 
teeth  in  the  opposite  jaw.  They  do  not  meet  end  on  end,  but  each 
tooth  is  in  relation  to  two  teeth.  The  exceptions  are  the  upper  third 
molar  and  the  lower  central  incisor  which  have  but  one  opponent 
each  (Fig.  89). 


224 


THE   TEETH  AS  A   MASTICATING  MACHINE 


Fig.  87. — Occlusion  of  the  molar  and  bicuspid  teeth,  external  view.     (From 
photograph  of  a  specimen  in  possession  of  Dr.  F.  A.  Peeso.) 


Fig.  88. — Occlusion  of  the  molar  and  bicuspid  teeth,  internal  view.     (From  photograph 
of  a  specimen  in  possession  of  Dr.  F.  A.  Peeso.) 


A  STUDY  OF  OCCLUSION 


225 


Now  that  the  relationship  of  the  morsal  or  occhisal  surfaces  of  the 
teeth  ill  the  position  of  occhisioii  has  been  described,  it  will  often  be 
referred  to  as  the  occlusion  of  the  teeth. 


Fig.  89. — Occlusion  of  the  molar  and  bicuspid  teeth,  occlusal  view.  Lines  are  drawn 
from  the  lingual  cusps  of  the  upper  teeth  and  buccal  cusps  of  the  lower  to  the  correspond- 
ing depressions  into  which  they  fit.  (From  photograph  of  a  specimen  in  possession  of 
Dr.  F.  A.  Peeso.) 

There  are  certain  other  characteristics  of  the  arrangement  of  the 
occlusal  surfaces  of  the  teeth  which  are  related  to  what  shall  be  spoken 


Fig.  90.- 


-The  "Curve  of  Spee."     Line  passing  through  anterior  face  of  condyle, 
a  photograph  of  a  specimen  in  the  Wistar  Institute  of  Anatomy.) 


(From 


of  as  the  articulating  or  active  relations  of  the  denture  that  will  be 
useful  when  the  denture  is  in  motion.     One  of  these  characteristics, 
15 


226  THE   TEETH  AS  A   MASTICATING  MACHINE 

which  is  a  very  important  part  in  the  so-called  articulation  of  the 
teeth,  is  as  follows:  If  an  imaginary  line  were  drawn  touching  the 
buccal  cusps  of  the  lower  series  of  teeth  in  a  perfect  denture,  it  would 
be  found  that  they  described  approximately  the  arc  of  a  circle,  and  if 
it  is  continued  backward  under  a  perfectly  typical  arrangement,  it 
passes  just  anterior  to  the  articulating  face  of  the  condyle  (Fig.  90). 
Sometimes  this  line  may  go  a  little  in  front  of  it,  more  frequently  it 
is  back  of  the  condyle;  in  a  perfect  arrangement  it  passes  through 
the  anterior  face  of  the  condyle.  The  same  thing  is  necessarily  true 
of  the  upper  teeth.  This  is  called  the  curve  of  Spec.  It  has  been 
named  after  von  Spec  who  first  called  attention  to  it.  This  curved 
arrangement  of  the  occlusal  surfaces  of  the  molar  and  bicuspid 
teeth  has  an  important  bearing  on  the  movement  of  the  mandible. 

If  two  surfaces  are  to  slide  one  upon  the  other  without  interrupting 
their  contact  at  any  point,  that  is,  without  being  separated  at  any 
point,  these  must  be  either  two  perfectly  flat  surfaces  like  two  panes 
of  plate  glass,  where  one  can  slide  upon  the  other  without  admitting 
air  underneath,  or  else  two  curved  surfaces  which  are  the  arcs  of  the 
same  circle.  If  they  were  any  other  shape,  as  for  example,  a  parabola 
or  hyperbola,  or  any  irregular  curve,  they  would  separate  at  some 
point.  Now  if  it  were  desirable  that  in  the  forward-and-backward 
movement  of  the  mandible  all  of  the  lower  teeth  should  slide  upon  all 
of  the  upper  at  the  same  time,  then  these  teeth  would  have  to  be  either 
in  a  perfectly  plane  surface,  all  absolutely  level,  or  they  would  have 
to  be  arranged  around  the  arc  of  a  circle. 

In  order  to  get  a  clearer  understanding  of  this,  it  may  be  supposed 
that  there  are  no  cusps  upon  the  occlusal  surfaces  and  that  a  curved 
line  represents  the  top  surface  of  the  lower  teeth,  and  a  similar  curved 
line  represents  the  occlusal  surfaces  of  the  upper  teeth.  Now  if  these 
surfaces  are  to  slide  upon  each  other,  withaut  breaking  their  contact, 
in  the  case  of  the  human  jaw  the  mandibular  condyles,  which  of 
course  slide  upon  the  glenoid  fossae,  would  havje  to  slide  in  exactly 
that  same  curve,  otherwise  the  teeth  would  be  separated  at  some 
point. 

Now  this  is  the  significance  of  this  arrangement  of  the  teeth,  that  the 
so-called  curve  of  Spec  is  always  either  continuous  with  the  path  of 
the  condyle,  or  it  is  concentric  with  it;  at  any  rate  they  can  both 
move  around  the  same  center.  This,  it  must  be  remembered,  is 
merely  a  very  much  simplified  example  taken  to  explain  the  principle 
involved.  These  are  not  plane  surfaces,  but'  are  cuspid  sm-faces, 
and  each  one  of  these  cusps  fits  into  a  fossa.  However,  it  does 
not  take  a  very  great  stretch  of  imagination  to  see  that,  though 
they  have  cuspid  surfaces,  the  cusps  may  be  arranged  so  that  instead 
of  sliding  upon  a  smooth  surface  they  slide  upon  the  walls  of  the  fossae 
into  which  they  fit.  That  it  is  possible  to  have  such  an  arrangement 
may  be  conceived  and  this  is  the  arrangement  in  the  perfectly  typical 
and  typal  human  denture.  Of  course  the  mandible  has  to  be  depressed 


CUSP  ARRANGEMENT  AS  RELATED  TO  JAW  MOVEMENT     227 

the  least  })it  in  order  to  enable  each  cusp  to  slide  downward  on  the 
front  wall  of  the  fossa  into  which  it  fits.  The  cusps  slide  forward  on 
the  walls  of  the  fossre  and  back  again;  and  the  advantage  of  this  is 
that  every  one  of  the  cusps  is  functionating,  is  in  contact  at  the  same 
time,  not  just  hitting  here  or  there.  But  it  is  possible  for  a  denture 
to  functionate  in  this  fashion  only  if  the  teeth  are  arranged  in  the 
manner  described. 

It  will  presently  be  seen,  however,  that  the  lower  teeth  of  a  normal 
typical  denture  cannot  slide  very  far  forward  without  the  teeth  separa- 
ting, because  the  lower  incisors  strike  the  lingual  surfaces  of  the  upper 
incisors.  After  the  cusps  have  moved  perhaps  half-way  up  the  walls  of 
the  fossaj  into  which  they  fit,  the  lower  front  teeth  strike  the  upper 


Fig.  91. — Upper  and  lower  bicuspid  and  molar  teeth  (side  view),  showing  relative 
height  of  buccal  and  lingual  cusps  of  upper  teeth.  (From  photograph  of  a  specimen 
in  the  Wistar  Institute  of  Anatomy.) 


incisors  upon  which  they  slide  and  the  distal  teeth  are  separated. 
But  in  the  return  movement,  when  the  lower  teeth  strike  the  lingual 
surface  of  the  upper  and  slide  up  until  the  distal  teeth  are  in  contact 
and  then  slide  back  into  the  occlusal  position,  each  one  of  the  cusps 
then  slides  back  dowai  the  wall  of  its  fossa  into  the  position  of  the 
occlusion. 

There  is  another  characteristic  of  the  arrangement  of  the  molar  and 
bicuspid  teeth  which  is  related  to  the  lateral  excursion  of  the  jaw. 
Taking  a  typically  perfect  set  of  teeth  with  the  jaws  slightly  apart, 
it  will  be  seen  that,  starting  from  the  first  upper  bicuspid  and 
going  toward  the  rear,  the  buccal  or  outer  cusps  become  relatively 
a  little  bit  shorter  than  the  lingual  cusps  and,  in  the  case  of  the 
lower  teeth,  they  become  a  little  longer  than  the  lingual  cusps.     Of 


228 


THE   TEETH  AS  A   MASTICATING  MACHINE 


the  second  bicuspid  in  the  upper  jaw,  the  buccal  and  lingual  cusps  nor- 
mally occupy  the  same  horizontal  plane.  Just  in  front  of  it  the  first 
bicuspid  has  a  buccal  cusp  that  is  longer  than  the  lingual.  Return- 
ing to  the  first  molar,  the  buccal  cusps  are  a  little  shorter  than  the 
lingual,  and  going  back  farther  and  farther,  they  get  relatively  shorter 
than  the  lingual.  In  other  words,  the  plane  of  the  cusps,  instead  of 
being  level,  gradually  curves  rootword  and  outward  toward  the  rear  qf 
the  denture  (Fig.  91). 

This  arrangement  can  be  demonstrated  in  the  mandible  although  the 
first  bicuspid  has  a  rudimentary  cusp  or  none  at  all  and  is  atypical  in 


Fia.  92. — Lower  bicuspid  and  molar  teeth,  front  view,  showing  relative  height  of 
buccal  and  lingual  cusps.  Same  mandible  as  Fig.  91.  (From  photograph  of  a  speci- 
men in  the  Wistar  Institute  of  Anatomy.) 

this  particular;  but  farther  back  the  buccal  cusps  are  relatively  higher 
than  the  lingual  until  at  the  third  molar  thev  are  considerably  higher 
(Fig.  92). 

In  looking  at  the  upper  teeth  this  characteristic  may  not  be  so  well 
illustrated  as  in  the  lower  jaw,  but  a  gradual  tilting  out  of  the  long 
axes  of  the  teeth  will  be  noted.  This  arrangement  is  due  not  only 
to  the  height  of  the  cusps,  but  to  a  change  in  the  inclination  of  the 
teeth.  The  second  bicuspid  occupies  a  perpendicular  position;  but 
the  teeth  back  of  it  gradually  tilt  outward. 

Now  what  is  the  relationship  of  this  arrangement  to  the  lateral 
excursion  of  the  lower  jaw?    When  the  mandible  is  moved  to  one  side 


CUSP  ARRANGEMENT  AS  RELATED  TO  JAW  MOVEMENT     229 

with  the  teeth  in  contact,  if  the  teeth  were  arranged  so  that  their  cnsps 
occupied  the  same  horizontal  phme  those  on  one  side  would  be  sepa- 
rated while  those  on  the  other  side  would  be  in  contact.  The  reason 
for  this  is  that  when  the  mandible  is  carried  to  one  side  one  condyle 
remains  stationary  in  its  fossa  while  the  other  is  pulled  forward  and 
also  downward  as  the  surface  of  the  glenoid  fossa  inclines  downward 
and  this  side  of  the  jaw  must  be  carried  a  little  lower  than  the  side 
with  the  stationary  condyle. 

If  it  were  not  for  this  difference  in  the  level  of  the  buccal  and  lingual 
cusps  there  would  be  a  lack  of  contact  on  the  side  from  which  the 
movement  was  taking  place.  In  order  to  compensate  for  this  lower- 
ing of  the  mandible  on  the  side  from  which  the  movement  has  taken 
place,  the  two  longest  or  most  prominent  cusps  come  into  contact; 
whereas  on  the  other  side,  the  side  toward  which  the  movement  has 
taken  place,  there  is  a  short  and  a  long  cusp  in  contact;  and  it  is  just 
the  difference  between  these  two  w^hich  compensates  for  the  down- 
ward movement  of  the  jaw  on  the  side  from  which  the  movement  has 
occiu-red  (Fig.  93). 


Fig.  93. — Diagram  illustrating  contact  of  cusps  in  lateral  excursion  of  the  mandible. 
Section  through  jaws  at  position  of  second  molar.  O  P,  line  touching  lingual  cusps  of 
upper  molars;  L  R,  line  touching  buccal  cusps  of  upper  molars;  S  T,  line  touching  buccal 
cusps  of  lower  molars,  showing  the  downward  movement  of  the  mandible  on  the  right 
side  necessary  for  contact  of  the  cusps. 

What  is  the  advantage  of  this  arrangment?  It  has  exactly  the  same 
functional  advantage  in  the  lateral  excursion  of  the  mandible  as  the 
curve  of  Spec  affords  in  the  forward  and  backward  excursion  of  the 
jaw;  that  is  to  say,  it  enables  both  sides  to  be  in  contact  at  the  same 
time.  This  principle  is  taken  advantage  of  in  making  artificial  dentures. 
If  both  sides  of  the  plates  were  not  in  contact  at  the  same  time,  so 
that  the  patient  was  biting  foods  on  one  side  with  the  other  side  not 
touching  at  all,  the  plates  would  be  thrown  douTi  from  their  base. 
So  it  is  desirable  to  imitate  the  human  denture  in  this  particular  because 
it  prevents  overstrain,  and  provides  a  denture  that  is  more  efficient 
mechanically. 

There  is  one  other  detail  of  the  occlusal  surfaces  of  these  teeth  relat- 
ing to  their  function  which  must  be  mentioned  and  this  is,  that  clear- 
ance spaces  are  provided  for  the  escape  of  food  which  has  been  masti- 


230  THE  TEETH  AS  A  MASTICATING  MACHINE 

cated.  The  upper  row  of  buccal  cusps  overhangs  the  lower,  and  on  the 
outer  walls  of  all  of  these  fossae,  into  which  the  lower  buccal  cusps  fit, 
are  grooves  leading  do^Miward  and  outward  through  which  the  food  is 
squeezed.  Anyone  operating  a  cutting  or  grinding  machine  of  any 
kind  will  realize  the  necessity  of  getting  rid  of  the  waste  or  the  chip, 
as  the  mechanical  terminology  is.  That  is,  after  the  substance  has 
been  crushed  or  ground,  there  must  be  an  avenue  of  escape  for  the 
waste,  and  so  these  grooves,  which  are  not  visible  on  the  side  view, 
but  which  lead  downward  on  the  outside  of  the  arch,  and  upward  on 
the  inside,  are  provided.  When  the  food  is  crushed  between  these 
surfaces  it  is  carried  up  above  the  tongue  on  the  inside  and  downward 
into  the  pocket  of  the  cheek  on  the  outside  where  it  may  be  pressed 
between  the  teeth  when  they  are  separated  for  the  next  crushing  motion. 

Mastication  of  Food. — Having  described  the  machine,  its  mode  of  opera- 
tion may  now  be  considered;  In  the  case  of  man  the  preparation  of 
food  in  the  mouth  does  not  begin  with  prehension  or  gripping  of  the 
food,  as  it  does  in  most  of  the  lower  animals.  Man  has,  of  course, 
developed  very  much  beyond  that  point,  and  there  is.  no  necessity  for  it. 
There  is  no  provision  for  this  in  his  denture  therefore,  and  he  has  no 
sharp  teeth  to  prehend  the  food.  The  first  act  of  the  human  animal  is 
to  incise;  but  even  incision  or  the  cutting  off  of  appropriately  sized 
particles  of  food  is  largely  rudimentary  in  man,  since  with  the  devel- 
opment of  conventional  methods  of  eating,  bringing  into  use  the  knife 
and  fork,  the  incisior  teeth  are  not  much  exercised.  The  biting  of  cer- 
tain articles  of  food  only  is  permitted  by  the  usages  of  polite  society. 
But  w^hen  incision  is  indulged  in  it  is  rather  an  interesting  mechanical 
act.  The  lower  jaw  is  depressed  and  carried  forward,  the  food  is  pressed 
between  the  lips  and  upon  the  incisal  edges  of  the  upper  teeth,  when  the 
lower  jaw  is  carried  upward.  If  the  food  is  very  hard,  the  ends  of  the 
upper  and  lower  teeth  are  almost  exactly  opposite  each  other.  This 
direct  opposition  is  absolutely  necessary  from  a  mechanical  stand- 
point, in  order  to  bite  through  hard,  resistant  food.  As  soon,  how- 
ever, as  the  teeth  come  into  contact,  or  nearly  into  contact,  the  man- 
dible is  carried  backward  as  well  as  upward,  and  the  lower  incisors 
slide  up  the  inner  surface  of  the  upper,  just  like  the  blades  of  a  pair  of 
shears.  Then  the  food  is  carried  back  by  the  tongue  to  the  distal  part 
of  the  mouth. 

In  order  to  understand  clearly  just  what  is  demanded  during  tritura- 
tion of  the  food,  it  will  be  wise  to  refer  again  to  the  importance  of  a 
knowledge  of  the  character  of  the  food  itself.  Its  chemical  nature  is 
not  of  so  much  interest  as  its  physical  character  viewed  purely  from 
a  mechanical  standpoint.  Man's  food,  broadly  speaking,  consists  of 
meat  fiber,  vegetable  fiber,  grain  or  cereals  and  foods  made  from  them, 
and  legumes,  although  the  last  is  not  of  the  same  importance  as  the 
others.  The  chief  articles  which  must  be  prepared  for  digestion  are 
vegetable  and  meat  fibers,  cereals  or  grain.  It  is  necessary  to  reduce 
this  food  to  a  condition  suitable  for  passage  into  the  stomach.    Its 


MASTICATION  231 

physical  consistence  must  be  reduced  that  it  can  be  acted  upon  by  the 
digestive  ferments  and  solvents.  The  crushing  of  grain,  the  starchy 
element  of  man's  food  must  be  very  much  more  extensive  than  is  neces- 
sary for  the  other  elements.  In  the  first  place,  its  outer  covering  has 
to  be  removed,  or  at  least  broken,  and  the  grains  of  starch  themselves 
must  be  so  ground  up  that  they  can  be  acted  upon  by  the  enzyme  of 
the  mouth,  and  l)y  those  farther  down  in  the  digestive  tract.  Masti- 
cation of  cereals  and  foods  made  from  them  is  therefore  really  much 
more  important  than  the  mastication  of  other  foods. 

Baron  Oefele  has  conducted  some  investigations  to  show  the  very 
poor  ability  to  digest  cereals  exhibited  by  people  who  do  not  have  a 
full  complement  of  molar  and  bicuspid  teeth.  His  results  are  very 
interesting,  but  it  is  only  necessary  for  our  purpose  to  state  the  fact 
that  he  has  very  conclusively  shown  the  defective  digestion  of  cereals 
by  those  whose  molar  and  bicuspid  teeth  are  defective. 

Vegetable  fibers  nuist  be  cut  uj)  into  short  lengths  and  crushed  so 
that  they  can  be  readil}'  acted  upon  by  the  solvents  and  digestive  fer- 
ments. This  is  more  important  than  the  comminution  of  meat  fibers. 
Many  carnivorous  animals  eat  animal  flesh  in  great  masses;  carnivor- 
ous snakes  always  swallow  their  prey  w^hole.  Nevertheless  it  is 
important  that  meats  should  be  masticated  by  man  in  order  to  break 
up  the  consistence  of  the  fibef,  and  also  it  should  be  cut  up  into  small 
masses  to  facilitate  its  passage  through  the  digestive  tract  and  that  it 
may  be  readily  acted  upon  by  the  enzymes  and  ferments. 

Dr.  Black,  who  has  investigated  quite  extensively  the  problem  of 
the  mastication  of  the  various  kinds  of  foods,  is  authority  for  the  state- 
ment that  the  up-and-down  movements  of  the  jaw,  very  much  like 
those  of  the  carnivorous  animals,  are  chiefly  concerned  in  the  masti- 
cation of  meats,  and  that  the  lateral  movements  are  chiefly  concerned 
in  the  mastication  of  cereals  and  foods  made  from  them. 

While  it  is  not  true  that  in  the  masticating  of  any  type  of  food  one 
is  limited  to  any  particular  type  of  movement,  it  is  a  fact  that  the 
foods  which  require  the  greatest  amount  of  crushing  force  are  masti- 
cated in  the  return  from  the  lateral  excursion  of  the  mandible. 

AVhen  the  cereal  food  is  brought  into  the  mouth  and  carried  back 
to  the  molar  and  bicuspid  teeth,  mastication  usually  occurs  on  one  side 
at  a  time;  and  if  the  mouth  is  in  a  state  of  balance  and  perfect  health,  it 
is  very  apt  to  occur  first  on  one  side  and  then  on  the  other.  The  man- 
dible is  carried  to  one  side,  the  cusps  are  brought  into  contact,  some 
of  the  food  being  cut  off  on  the  outside  and  some  on  the  inside,  but  a 
mass  remains  which  occupies  the  space  between  the  cusps  and  in  the 
fossae  and  on  the  return  to  the  position  of  occlusion  the  cusps  slide, 
into  the  fossae  with  a  sort  of  mortar-and-pestle  effect.  In  this  movement 
the  greatest  crushing  ability  is  exhibited.  In  ordinary  mastication  this 
lateral  movement  is  combined  with  direct  up-and-down  movement. 
Mastication  is  not  carried  on  in  any  precise  mechanical  order,  but  all 
of  the  movements  are  combined  at  times. 


232  THE   TEETH  AS  A  MASTICATING  MACHINE 

Dr.  Black  has  also  made  in  this  connection  what  is  rather  an  interest- 
ing table  of  the  amount  of  force  necessary  to  crush  the  various  foodstuffs. 
Dr.  Joseph  Head,  of  Philadelphia,  has  also  produced  a  similar  table, 
though  using  a  different  method,  and  the  two  will  be  presented  together. 
Dr.  Black's  experiments  were  most  interesting.  He  had  some  brass 
castings  made  of  the  molar  and  bicuspid  series  of  teeth,  upper  and 
lower,  and  had  them  arranged  in  a  machine  so  that  the  lower  could 
be  brought  up  into  contact  with  the  upper  by  the  movement  of  a  hand 
lever:  This  simply  had  the  up-and-down  motion.  He  and  a  party  of 
friends  went  at  various  times  to  restaurants  in  Chicago,  and  while  they 
were  dining  themselves,  they  gave  this  automatic  chewing  machine 
various  tidbits,  and  registered  on  it,  as  they  could  not  on  their  own 
jaws,  the  amount  of  force  necessary  to  crush  the  various  foodstuffs. 

Dr.  Head,  realizing  the  value  of  the  lateral  excursion,  and  believing 
that  much  less  force  was  required  in  the  crushing  of  food  with  this  type 
of  movement,  made  experiments  similar  to  those  of  Dr.  Black,  except 
that  he  took  a  human  skull  with  a  fine  set  of  teeth  and  turned  it  upside 
down,  bored  a  hole  through  the  skull,  and  suspended  weights  from  the 
mandible  by  means  of  string  or  wire.  He  proved  that  to  accomplish 
the  same  amount  of  crushing,  less  force  was  required  in  this  lateral 
sliding  movement.    Dr.  Black's  and  Dr.  Head's  tables  are  here  given. 

Dr.  Head's  Dr.  Black's 

results.  results. 

Raw  cabbage 16  40-60 

Raw  onion 4 

Head  lettuce 8  25-30 

Radish— whole 20-25 

Radish— pieces 10-25  35-40 

Corned  beef 18-20  30-35 

Boiled  beef 3 

Tongue 1-2  3-5 

Lamb  chops ■    .      .      .      16-20 

Roast  lamb 4 

Roast  lamb  kidney 3 

Tenderloin  of  beefsteak  (ver>'  tender)      ....        8-9  35-40 

Sirloin  steak 10-20-43 

Round  of  beefsteak  (tough) 38-42  60-80 

Roast  beef 20-35  35-50 

Boiled  ham 10-14  40-60 

Pork  chops 10-13 

Roast  veal 16  35-40 

Veal  chops 12 

Roast  mutton 18-22 

Very  tough  meats 90 

Hard  crusts 100 

Hard  candy        250 

Dr.  Black  also  experimented  with  a  gnathodynamometer  by  means 
of  which  he  could  measure  the  strength  exerted  by  the  human  dental 
mechanism,  which  for  the  average  was  from  150  to  175  pounds.  He 
reported  one  case  in  ^^•hich  275  pounds  were  recf)rded  on  the  instru- 
ment. He  also  tried  it  with  persons  wearing  full  artificial  dentures, 
upper  and  lower,  the  result  being  that  the  average  was  from  35  to  40 


MASTICATION  233 

pounds.  One  may  see  a  vast  (liflerence  in  the  amount  of  crushing 
ahihty  of  natural  and  artificial  teetli. 

INIastication  is  of  course  a  vohuitary  act  (si)eaking  physiologically), 
that  is,  it  begins  voluntarily  and  is  continued  refiexly  and  automatic- 
ally. The  food  is  rolled  from  one  side  to  the  other  by  the  tongue. 
The  teeth  functionate  first  on  one  side  and  then  on  the  other.  The 
teeth  have  exquisite  sensibility.  It  is  through  them  that  sensations 
are  received  that  indicate  the  amount  of  chewing  necessary  to  give 
any  given  mouthful,  and  also  through  them  in  conjunction  with  the 
tongue  as  to  whether  the  food  has  l)een  thoroughly  triturated  or  not. 
After  it  has  been  thoroughly  masticated  it  is  rolled  up  into  a  bolus  on 
the  tongue,  the  tip  of  which  is  elevated,  and  by  contraction  of  the 
muscle  of  the  floor  of  the  mouth,  the  mylohyoid,  the  food  is  forced 
back  into  the  esophagus. 

The  secretion  of  the  saliva,  while  constantly  going  on  in  the  mouth, 
is  tremendously  increased  when  any  foreign  substance,  like  food,  is 
put  into  the  mouth.  The  working  of  the  muscles  moving  the  jaw 
probably  also  increase  the  flow  of  saliva.  The  saliva  serves  to  lubri- 
cate the  various  portions  of  the  apparatus  which  are  in  the  mouth. 
It  contains  a  ferment,  ptyalin,  which  has  some  digestive  usefulness. 
The  water  in  the  saliva  dissolves  some  of  the  food,  and  as  it  also  con- 
tains mucin,  the  latter  helps  to  agglomerate  the  mass  and  to  lubricate 
it  so  that  it  is  finally  easily  swallowed. 

The  teeth  are  equipped  with  means  of  resisting  the  wear  incident 
to  the  activity  of  this  mechanism.  The  enamel  is  the  outer  envelope 
of  the  crowns  of  the  teeth  and  is  the  hardest  structure  in  the  human  body. 
It  is  of  course  necessary  to  have  a  very  hard  covering  for  the  teeth  to 
enable  them  to  resist  the  wear  incident  to  their  long  use.  Under  present 
conditions  of  civilization,  where  comparatively  little  mastication  is  neces- 
sary, not  a  great  deal  of  wear  of  the  teeth  occurs.  The  teeth  of  prehis- 
toric man,  and,  indeed,  of  our  own  aboriginal  races,  wore  very  badly  from 
the  coarse  character  of  the  food.  Any  collection  of  skulls  of  North  Amer- 
ican Indians  which  one  may  happen  to  see  at  once  impresses  one  wdth 
the  great  amount  of  wear  of  these  teeth.  Of  course  this  is  due,  not  only 
to  the  rough  character  of  the  food,  but  also  to  the  fact  that  Indian  corn, 
a  staple  diet,  being  ground  in  stone  mortars  had  fine  particles  of  stone 
or  silica  mixed  with  it,  which  serve  to  grind  the  teeth  down. 

Anatomists  have  recognized  several  degrees  of  wear.  No  one  reaches 
the  age  of  twenty-five  without  beginning  to  show  some  evidence  of 
wear  of  the  teeth.  A  little  later  the  second  degree  is  reached,  where 
the  enamel  is  worn  through  and  the  dentin  exposed,  and  the  cusps 
are  really  beginning  to  wear  down  a  little;  or  it  may  even,  under  con- 
ditions of  our  civilization,  get  to  the  third  degree,  where  the  cusps  are 
all  worn  away,  and  the  teeth  are  reduced  in  height. 

Mastication  has  also  a  beneficial  influence  upon  the  teeth.  The 
friction  of  the  food  exerts  a  cleansing  influence  as  regards  colonies 
of  bacteria  and  deleterious  food  particles  upon  their  surface.     Disuse 


234 


THE   TEETH  AS  A   MASTICATING  MACHINE 


of  the  teeth  on  the  other  hand,  greatly  increases  the  deposits  of  sali- 
vary calculus  and  sordes  upon  the  teeth.  Often  upon  looking  into 
a  mouth  it  is  perfectly  easy  to  judge  upon  which  side  a  crippled 
tooth  exists,  because  when  the  chewing  is  done  on  the  other  side, 
exclusively,  deposits  on  the  teeth  of  the  crippled  side  identify  it. 

The  use  of  the  denture  in  mastication  also  exercises  the  peridental 
membrane.  As  the  teeth  move  up  and  down  in  their  sockets,  blood  is 
pumped  in  and  out  of  this  tissue  and  thus  it  is  kept  in  a  healthy 
condition  and  degeneration  of  the  pericementum  is  deferred  if  not 
prevented. 

Supplementary  Functions  of  the  Teeth. — In  conclusion,  certain  second- 
ary functions  of  the  teeth  will  be  briefly  considered.    They  participate 


rK&Q. 


Fig.  94. — 1,  diagrammatic  drawing  showing  place  of  articulation  of  the  consonant 
sounds:  2,  drawing  showing  contact  of  the  tongue  with  molars  and  bicuspids  in  the 
formation  of  certain  consonants. 


in  the  activity  of  the  mechanism  concerned  in  the  production  of  speech. 
The  lijjs  and  tongue  with  the  teeth  and  the  contiguous  portions  of  the 
aheolar  process  are  the  most  important  factors  in  the  production  of 
consonant  sounds.  Thus  the  "F"  and  "V"  sounds,  for  example,  are 
pronounced  by  the  sudden  escape  of  air  between  the  lower  lip  and  the 
upper  front  teeth.  It  is  unnecessary  to  go  into  this  detail  at  length,  but 
an  alhision  is  made  to  it  as  an  additional  reason  for  care  in  the  preserva- 
tion of  the  teeth  (Fig.  94). 

They  are  al.so  passive  elements  in  the  mechanism  concerned  with  the 
facial  movements  of  expression,  which  are  movements  of  the  facial 
muscles  that  either  supplement  language  or  convey  ideas  or  emotions 
or  states  of  mind. 


SUPPLEMENTARY  FUNCTIONS  OF  THE   TEETH  235 


«VATOR 
ANGULI      \i; 
SWPEHIOBIS 


Fig.  95. — The  facial  muscles  of  expression. 


r " 

P^ 

^^^^^1 

^^^^H 

El 

[ 

Fig.  96. — Photograph  showing  effect 
of  the  loss  of  the  teeth  upon  the  mouth, 
and  wrinkles  established  thereby. 


Fig.  97. — Photograph  showing  the 
effects  of  the  loss  of  the  teeth  upon  the 
profile. 


236  THE   TEETH  AS  A   MASTICATING  MACHINE 

The  underlying  structures  in  this  mechanism  are  the  skull  and  the 
teeth,  overlying  which  are  soft  tissues  including  the  facial  muscles  of 
expression.  There  is  a  large  group  of  these  centering  around  the  mouth 
which  makes  it  one  of  the  most  expressive  features  of  the  face.  These 
muscles  are  superficial,  converge  toward  the  mouth  and  terminate  in 
one  big  muscle,  the  orbicularis  oris,  of  which  latter  the  lips  are  chiefly 
composed.  These  are  all  supported  beneath  by  the  teeth  and  the 
alveolar  process,  over  which  as  a  sort  of  base  they  are  moved  by  these 
various  muscles.  In  some  of  these  movements  the  lips  are  parted  so 
that  the  teeth  are  disclosed.  Both  pleasurable  and  painful  emotions 
may  be  so  exjDressed  (Fig.  95). 

Finally  the  teeth  serve  to  support  the  lips  and  the  cheeks  and  thus 
take  part  in  the  maintenance  of  the  fixed  expression  of  the  face. 
Their  loss  is  attended  by  a  falling  in  of  these  tissues,  an  approxi- 
mation of  the  jaws,  and  by  a  marked  change  in  the  appearance  in  the 
face.  To  guard  against  this  "last  scene  of  all"  is  the  final  reason  for 
their  preservation  (Figs.  96  and  97). 


CHAPTER   IX. 
MALOCCLUSION  OF  THE  TEETH 

By  RODRIGUES  OTTOLENGUI,  M.D.S.,  D.D.S.,  LL.D. 

If  the  mouth  hygienist,  besides  preserving  the  heahh  of  her  charge, 
would  aim  likewise  to  guard  against  the  attacks  of  disease,  it  is  evident 
that  she  should  have  knowledge  of  such  diseases  as  may  prove  a  menace 
in  her  particular  field  of  work,  and  she  should  likewise  learn  to  recog- 
nize these  diseases  in  their  incipient  stages  that  she  may  refer  the 
patient  for  treatment  before  the  ravages  prove  serious. 

Therefore,  in  presenting  the  subject  of  malocclusion,  let  us  consider 
for  a  moment  how  dental  caries  is  aggravated  by  irregular  or  mal- 
occluded  teeth. 

DENTAL   CARIES 

Areas  of  Susceptibility. — Students  of  the  subject  tell  us  that  in  the 
vast  majority  of  cases  caries  begins  in  certain  definite  localities. 
Thus  caries  upon  the  masticating  surfaces  of  bicuspids  and  molars 
first  appears  in  the  sulci  or  fissures  between  the  enamel  plates. 
Between  the  teeth  or,  as  we  say,  on  the  approximal  surfaces,  caries 
has  its  initiation  at,  or  just  gingival  to,  the  approximal  contact 
points.  While  it  may  not  be  absolutely  true  that  "a  clean  tooth 
never  decays,"  it  is  true  that  an  unclean  tooth  is  more  vulnerable  than 
one  that  is  clean.  It  follows,  therefore,  that  the  unclean  or  uncleans- 
able  parts  of  a  tooth  are  more  likely  to  decay  than  the  clean  or 
readily  cleansable  parts  of  a  tooth,  and  this  is  in  consonance  with  the 
statements  above  made  as  to  the  locations  where  caries  usually  begins, 
because  the  sulci  of  molars  and  bicuspids,  and  the  approximal  con- 
tact points  of  all  teeth,  are  the  localities  in  which  food  debris  is  most 
apt  to  lodge  and  most  difficult  to  dislodge.  Another  region  in  which 
caries  often  occurs  is  upon  the  labial  and  buccal  surfaces  of  teeth 
immediately  near  the  gum  line.  Here  the  seepage  of  mucus  agglu- 
tinizes  the  food  debris  and  the  overhanging  gum  margins  protect  the 
accumulations  from  the  natural  cleansing  agents.  Still  another  place 
is  in  the  grooves  on  the  buccal  siu-faces  of  the  molars,  which  are 
analogous  with  the  sulci  upon  the  masticating  surfaces.  These,  then, 
are  to  be  counted  the  vulnerable  places. 

Areas  of  Immunity. — The  lingual  surfaces  of  all  the  teeth,  swept  as 
they  are  by  the  tongue,  constitute  the  most  immune  areas,  though 
occasionally  we  find  pits  or  crevices  in  the  upper  mcisors,  which 
because  they  are  pits  or  crevices  become  susceptible  points.  The 
labial  surfaces  of  all  incisors  and  cuspids,  except  at  or  along  the  gum 


238  MALOCCLUSION  OF   THE  TEETH 

margins,  and  the  buccal  surfaces  of  all  molars,  •  except  in  the  buccal 
grooves,  are  practically  immune  to  caries. 

So  we  find  that  there  are  certain  localities  which  are  vulnerable  and 
other  definite  parts  of  the  tooth  which  are  practically  immune  to  caries. 
Also,  that  this  immunity  is  closely  related  to  the  possibility  of  cleans- 
ing these  areas. 

Between  these  vulnerable  and  immune  locations  are  areas  of  com- 
parative immunity,  this  comparative  immunity  increasing  toward 
the  immune  or  most  easily  cleansed  part,  and  decreasing  as  we  approach 
the  vulnerable  or  less  easily  cleansed  part. 

Caries  and  Malocclusion. — Thus  we  arrive  at  the  important  relation 
between  malocclusion  and  caries.  We  have  seen  that  certain  parts  of 
the  teeth  are  counted  to  be  immune  to  caries,  and  that  adjacent  to 
these  areas  are  other  parts  which  are  comparatively  immune.  But 
this  is  true  only  when  all  the  teeth  are  in  normal  relationship  one 
with  the  other,  which  in  effect  means  when  all  the  teeth  are  in 
normal  occlusion. 

^Malocclusion  may  not  perhaps  often  increase  the  vulnerability  of 
the  occlusal  surfaces  of  the  teeth,  though  at  times  it  may  even  have 
this  effect;  but  malposition  of  the  teeth  will  frequently  increase  the 
vulnerable  approximal  areas  by  increasing  the  con  tactual  areas  beyond 
the  normal;  and  it  will  likewise  lessen  the  immunity  of  the  immune 
and  comparatively  immune  areas,  by  rendering  cleansing  more  diffi- 
cult and  at  times  even  impossible. 

We  will  better  comprehend  this  by  the  examination  of  a  skull  where 
we  may  see  the  teeth  and  bones  freed  from  the  soft  tissues. 

Interproximal  Spaces.  Fig.  98  affords  a  good  example  of  normally 
occluded  teeth,  one  maxilla  and  one-half  of  the  mandible  with  their 
teeth  being  shown.  Attention  should  be  called  first  to  the  spaces  between 
the  teeth  knowTi  as  interproximal  spaces.  Note  that  these  are,  gener- 
ally speaking,  triangular  in  shape,  the  base  of  the  triangle  being  along 
the  border  of  the  alveolar  bone,  the  sides  of  the  triangle  being  the 
approximal  surfaces  of  the  adjacent  teeth,  and  the  apex  at  the  point 
of  contact  of  the  two  teeth.  Select  any  approximal  space  distal  of 
the  cuspids  and  note  that  the  apex  of  the  cusp  of  the  antagonizing 
tooth  of  the  opposing  jaw  falls  immediately  opposite  the  center  of 
this  interproximal  space,  the  obvious  tendency  being  to  force  food 
between  the  teeth,  and  into  this  interproximal  space.  Hence  the  need 
of  the  contact  point.  Passing  from  the  study  of  these  bones  and  exam- 
ining a  living  specimen,  we  would  observe  that  this  interproximal  space 
is  filled  with  gum  tissue,  this  particular  part  of  the  gum  being  denomi- 
nated the  septum.  This  septum,  filling  as  it  does  a  triangular  space, 
is  conical  in  shape  and  is  thicker  than  other  parts  of  the  gum.  For  this 
reason  its  outer  surface  is  farther  away  from  its  bony  support  and  con- 
sequently it  is  more  easily  injured  than  the  gum  elsewhere.  This  is 
an  added  need  for  close  contact  of  the  adjacent  teeth,  as  a  protection 
to  this  sensitive  tissue  from  the  impaction  of  food  and  the  retention 


DENTAL  CARIES 


239 


of  it,  if  forced  into  the  interproximal  space.  The  student  should  note 
also  that  the  gum  septum,  also  called  the  gingiva,  even  in  the  healthiest 
subject,  does  not  entirely  fill  the  interproximal  space,  so  that  commonly 
there  is  a  small  but  actual  space  between  the  approximal  contact 
points  and  the  septum  or  gingiva.  It  is  because  of  this  fact  that 
approximal  caries  often  has  its  inception  just  gingivally  of  the  con- 
tact point,  since  it  is  just  hi  this  space  which  is  protected  from  the 
natural  cleansing  agencies  that  debris  may  collect  and  remain. 

If  we  study  the  matter  more  closely  still,  we  must  see  that  wise 
provision  has  been  made  for  the  exclusion  of  foodstuffs  from  the  inter- 


FiG.  98. — Occlusion  of  the  molar  and  bicuspid  teeth,  external  view.     (From  photograph 
of  a  specimen  in  possession  of  Dr.  F,  A.  Peeso.) 

proximal  spaces.  True  the  grinding  cusps  of  the  masticating  teeth, 
falling  as  they  do  exactly  opposite  to  the  entrances  to  the  interproxi- 
mal spaces,  would  seem  to  be  advantageously  situated  for  the  forcing 
of  food  into  these  spaces,  yet  this  accident  is  well  guarded  against. 
First  we  find  that  the  cusps  in  typically  formed  teeth  occlude  against 
the  mesial  and  distal  marginal  ridges  of  the  two  teeth  with  which  each 
cusp  normally  antagonizes.  These  marginal  ridges  have  planes  slop- 
ing toward  the  central  portions  of  the  masticating  surfaces,  and  hence 
away  from  the  interproximal  space. 

^Moreover  we  find  sulci  serving  as  sluicew'ays  to  lead  the  food,  during 
maceration,  lingually  and  buccally  away  from  the  spaces  between  the 


240  MALOCCLUSION  OF  THE   TEETH 

teeth,  and  consequently  it  should  require  more  force  to  crowd  the  food 
into  the  interproximal  spaces  than  away  from  them  into  and  out  of 
the  sluiceways.  Additional  protection  of  the  gingivse  is  to  be  found  in 
the  form  and  position  of  the  contacts,  as  well  as  in  the  form  of  the  sep- 
tum itself.  The  contacts  are  closest  occlusally  and  triangular  in  shape 
so  that  the  width  of  the  contacts  increase  slightly  toward  the  gingiva, 
while  the  approximal  surfaces  of  the  teeth,  curving  rapidly  apart, 
afford  ample  opportunity  for  the  escape  of  food,  especially  as  the  sep- 
tum itself  is  conical  and  full  enough  buccolingually  to  extend  some- 
what beyond  the  actual  interproximal  space  and  thus  aid  in  receiving 
and  carrying  the  food  away  from,  rather  than  into,  the  space. 

All  this  may  seem  somewhat  complex,  whereas  in  reality  when  once 
fully  comprehended,  it  will  be  seen  to  be  quite  simple  and  as  admirable 
an  arrangement  as  it  is  a  simple  one.  Yet  its  efficiency  depends  entirely 
upon  and  is  proportional  with  its  typical  normality.  Any  aberration 
from  the  typical  in  the  formation  of  the  teeth,  and  any  departure  from 
the  normal  in  the  position  of  the  teeth,  must  proportionately  destroy 
the  balance  between  the  several  factors  which,  when  present  and  work- 
ing in  unison,  will  afford  ample  protection  to  even  this  vulnerable 
locality. 

Contact  Points  in  Normal  Arrangement. — Glancing  again  at  Fig.  98, 
the  student  is  asked  to  note  that  the  teeth  being  in  normal  arrange- 
ment, the  contacts  are  at  the  minimum,  while  yet  being  sufficient  to 
afFord  protection.  Since  caries  starts  at  these  points  of  contact,  it 
must  be  manifest  that  any  malposition  of  the  teeth  which  will  bring 
into  contact  a  greater  area  than  normally  should  be  in  contact,  not 
only  increases  the  actual  area  of  the  vulnerable  region,  but  by  altering 
the  protective  form  of  the  contact  points,  must  necessarily  add  also  to 
the  vulnerability.  In  Fig.  98  note  also  that  as  each  tooth  is  in  its  nor- 
mal pose  the  greater  portion  of  its  exposed  surface  is  brought  into 
symmetrical  alignment  with  its  neighbors,  so  that  any  cleansing  agency 
sweeping  around  the  arch  would  come  into  touch  with  and  conse- 
quently would  cleanse  the  greatest  width  of  such  surface.  Thus, 
where  teeth  are  normally  placed,  a  brush  passing  around  the  arch  would 
cleanse  nearly  all  the  labial  and  buccal  enamel,  while  a  brush  passed 
vertically  over  these  surfaces  would  cleanse  them  entirely.  An  exam- 
ination of  the  lingual  surfaces  (Fig.  99)  discloses  the  fact  that  the  truly 
normal  arrangment  again  brings  beneath  the  influence  of  a  cleansing 
agent  the  widest  expanse  of  surface. 

It  is  equally  evident  that  any  malposition  of  even  a  single  tooth  must 
interfere  with  this  cleansing  effort.  If  a  tooth  be  turned  upon  its  axis, 
then  a  smaller  part  of  its  labial  or  l)uccal  surface  can  be  swept  by  the 
brush  when  the  brush  is  used  upon  that  part,  and  the  same  would  be 
true  when  brushing  the  lingual  surfaces.  If  a  tooth  extends  beyond 
its  neighbors,  either  buccally  or  lingually,  not  only  will  it  become  more 
difficult  to  cleanse  that  particular  tooth,  but  its  position  must  inter- 
fere more  or  less  with  the  cleansing  of  its  neighbors. 


NOMENCLATURE  241 

It  is  seen  then  that  any  aberration  from  the  normal  in  the  inter- 
relation of  the  teeth  renders  them  more  difficult  to  keep  clean,  but  it 
must  be  understood  that  aside  from  the  artificial  cleansing  which  is 
to  be  accomplished  with  brushes,  powders,  etc.,  the  typical  forms  and 
arrangement  of  the  teeth  are  such  that  the  normal  use  of  these  organs 
leaves  them  moderately  clean,  so  that  the  teeth  in  ideal  normal  occlu- 
sion are  said  to  be  "self-cleansing,"  this  cleansing  being  accomplished 
by  the  lips,  the  tongue,  and  by  the  food  passing  over  the  surfaces  of 
the  teeth. 


Fig.  99. — Occlusion  of  the  molar  and  bicuspid  teeth,  internal  view.     (From  photograph 
of  a  specimen  in  possession  of  Dr.  F.  A.  Peeso.) 

Terms  Defined. — Occlusion:  The  relation  between  the  upper  and 
lower  teeth  when  the  jaws  are  closed. 

Arch:    A  term  used  to  designate  the  upper  or  lower  teeth  collectively. 

Inclined  Plane:    The  sloping  sm-face  of  a  cusp. 

Mesial,  Distal:  Position  is  considered  in  relation  to  the  median 
line  or  center  of  the  dental  arches.  Hence,  "mesiaF'  means  toward  or 
nearest  to  the  median  line,  and  "distal"  means  away  from  or  farthest 
from  the  median  line. 

Model:  A  reproduction  of  the  dental  arch  or  arches  made  in  plaster 
of  Paris. 

Labial:    Toward  the  lips. 

Buccal:    Toward  the  cheek. 
16 


242  MALOCCLUSION  OF  THE  TEETH 

Lingual:  Toward  the  tongue.  This  term  is  used  to  describe  the 
upper  as  well  as  the  lower  teeth. 

Protruding:  The  tipping  of  the  axis  of  a  tooth  so  that  the  crown 
projects  labially  to  normal. 

Retruding:  The  tipping  of  the  axis  of  a  tooth  so  that  the  crown 
slants  lingually  to  normal. 

A   STUDY   OF  NORMAL  OCCLUSION. 

Before  the  student  can  comprehend  any  description  of  malocclusion 
he  must  acquire  a  knowledge  of  normal  occlusion.  He  should  be  able 
mentally  to  visualize  a  set  of  teeth  in  normal  occlusion,  as  a  standard 
picture  with  which  to  compare  any  set  of  teeth  under  examination, 
in  order  instantly  to  detect  deviations  from  the  normal. 

Definition. — Normal  occlusion  is  the  normal  relation  of  the  occlusal 
inclined  planes  of  the  teeth  when  the  jaws  are  closed  (Angle) . 

As  occlusion  means  the  relation  betw^een  the  upper  and  lower  teeth 
when  the  jaws  are  closed,  it  follows  that  normal  occlusion  means  that 
all  the  teeth  in  both  arches  are  so  situated  that  they  may  best  perform 
their  functions,  and  that  their  interrelation  shall  be  typical  and  there- 
fore normal. 

In  a  set  of  teeth  in  normal  occlusion  the  teeth  themselves  are  arranged 
in  symmetrical  parabolic  curves,  commonly  called  arches.  This  means 
that  if  a  line  be  drawn  across  either  arch,  so  as  to  touch  the  distal  sur- 
faces of  the  last  molars,  and  a  second  line  be  drawn  at  right  angles 
thereto  and  through  the  median  space,  or  between  the  central  incisors, 
then  any  two  similar  teeth  on  opposite  sides  of  the  arch  (as  for  example 
the  first  bicuspids)  will  be  equidistant  from  this  central  line. 

Perhaps  the  next  most  noteworthy  fact  is  that  the  upper  arch  is 
slightly  larger  than  the  lower,  and  that  the  outer  cutting  edges  and 
cusps  of  the  upper  teeth  droop  over  and  consequently  hide  in  part  the 
similar  portions  of  the  lower  teeth  Mdien  the  jaws  are  closed  (Fig.  98). 
This  latter  condition  is  called  the  "overbite." 

In  a  full  denture  there  are  thirty-two  teeth.  In  the  illustration  which 
depicts  one-half  of  an  upper  and  lower  jaw  we  should  see  sixteen  teeth; 
but,  as  a  matter  of  fact,  the  artist  in  endeavoring  to  expose  the  full 
surface  of  the  upper  central  incisor  has  so  turned  the  subject  that  in 
the  lower  arch  we  see  an  extra  tooth,  the  lower  central  incisor  of  the 
opposite  side.  Mentally  eliminating  this  extra  tooth,  by  studying 
the  illustration  we  observe  that  the  smallest  incisor  is  the  central 
incisor  in  the  lower  arch,  while  the  smallest  molar  is  the  last  or  third 
molar  in  the  upper  arch.  It  is  in  accordance  with  Nature's  wonderful 
design,  which  aims  to  produce  the  highest  efficiency  in  the  use  of  the 
teeth  collectively  as  a  masticating  apparatus,  that  this  is  true,  for  by 
this  means  every  other  tooth  except  these  four  occludes  with  two  others. 
Again  glancing  at  the  illustration  we  see  that  the  lower  lateral  incisor 
is  in  contact  with  the  upper  central  and  lateral;  the  upper  central 


A  STUDY  OF  NORMAL  OCCLUSION  243 

touches  the  lower  central  and  lateral;  the  upper  lateral  antagonizes 
the  lower  lateral  and  cuspid,  and  so  on  around  the  arch,  each  tooth 
of  either  upper  or  lower  jaw  occluding  with  two  teeth  in  the  opposing 
jaw.  The  most  important  usefulness  of  this  arrangement  is  seen  when 
we  consider  those  teeth  which  have  cusps.  For  example,  observe  the 
first  upper  bicuspid,  occluding  wnth  the  cuspid  and  bicuspid  of  the 
lower  arch.  Any  food  caught  in  this  locality  is  triturated  between 
three  powerful  cusps,  a  much  more  effective  plan  than  were  each  tooth 
to  strike  only  one  antagonist,  as  sometimes  occurs  where  malocclusion 
is  present. 

This  at  once  brings  us  to  one  diagnostic  point.  It  being  a  fact  that 
in  normal  occlusion  all  the  teeth  except  the  lower  central  incisors  and 
upper  third  molars  occlude  so  that  each  tooth  antagonizes  two,  we 
note  that  the  only  place  in  the  entire  denture  where  the  interproximal 
spaces  coincide  is  at  the  median  line.  Two  facts  then  may  be  remem- 
bered. Whenever  any  interproximal  spaces  above  and  below  coincide 
(except  these  at  the  median  line),  malocclusion  exists.  Conversely, 
whenever  the  spaces  at  the  median  line  do  not  coincide,  malocclusion 
is  present. 

We  should  next  consider  those  teeth  which  are  supplied  with  cusps, 
viz.,  the  cuspids,  the  bicuspids  and  the  molars.  In  regard  to  the  cus- 
pids and  bicuspids,  when  in  normal  occlusion  the  crest  or  extreme 
angle  of  the  cusp  should  be  exactly  in  line  with  the  interproximal 
space  between  the  two  teeth  with  which  it  occludes.  Or  to~  phrase  it 
differently,  a  line  drawn  through  the  central  axis  of  a  cuspid  or  bicus- 
pid should  pass  between  the  two  antagonizing  teeth. 

In  all  the  teeth  which  have  cusps,  including  the  molars,  each  cusp 
has  four  slanting  surfaces  called  inclined  planes;  note  that  of  these  the 
mesial  inclined  planes  of  the  cusps  of  the  upper  teeth  occlude  with  the 
distal  inclined  planes  of  the  cusps  of  the  lower  teeth;  and  of  course 
the  distal  inclined  planes  of  the  upper  cusps  touch  the  mesial  inclined 
planes  of  the  lower  teeth. 

As  will  be  seen  presently,  however,  a  point  of  extreme  significance, 
because  used  so  often  as  a  basis  of  diagnosis,  is  the  occlusal  relation  of 
the  upper  and  lower  first  molars.  The  student  therefore  should  become 
thoroughly  familiar  with  this  cusp  relation  (Fig.  9S).  The  upper  molar 
has  two  buccal  cusps,  known  as  the  mesiobuccal  cusp  and  the  disto- 
buccal  cusp.  In  normal  occlusion  the  mesiobuccal  cusp  of  the  upper 
first  molar  occludes  between  the  mesiobuccal  and  buccal  cusps  of  the 
lower  first  molar,  in  such  a  manner  that  the  crest  or  extreme  point  of 
the  cusp  coincides  with  a  groove  in  the  buccal  surface  of  the  lower 
tooth,  known  as  the  buccal  groove.  It  is  w^ell  also  to  observe  that  the 
mesiobuccal  cusp  of  the  lower  molar  occludes  in  part  with  the  similar 
cusp  of  the  upper  molar  and  in  part  with  the  upper  second  bicuspid; 
also  that  the  extreme  mesial  surface  of  the  lower  molar  is  on  a  line  with 
the  central  axis  of  the  upper  second  bicuspid.  Attention  is  called  to 
this  fact  here,  as  it  will  be  again  elsewhere,  because  while  in  the  normal 


244  MALOCCLUSION  OF   THE   TEETH 

relation  the  lower  first  molar  is  slightly  mesial  of  the  upper  first  molar, 
it  should  not  be  farther  forward  than  the  median  axis  of  the  upper 
second  bicuspid. 

A  study  of  the  same  set  of  teeth  from  the  lingual  aspect  (Fig.  99), 
shows  similar  interlocking  of  the  teeth  and  the  general  appearance  is 
the  same  except  that  here  it  is  the  cusps  and  incisal  ends  of  the  upper 
teeth  that  are  slightly  hidden  in  consequence  of  the  overbite,  the 
converse  of  what  is  true  of  the  buccal  view  (Fig.  98). 

Summary. — 1.  Where  teeth  are  in  normal  occlusion  they  are  arranged 
in  symmetrical  parabolic  curves  and  any  two  similar  teeth  on  opposite 
sides  of  an  arch  will  be  equidistant  from  the  central  line,  or  axis. 

2.  The  upper  arch  is  larger  than  the  lower  and  the  cusps  of  the  upper 
teeth  droop  over  the  lower.    This  is  denominated  the  overbite. 

.3.  With  the  exception  of  the  two  lower  central  incisors  and  the 
two  upper  third  molars,  each  tooth  in  each  arch  antagonizes  with  two 
teeth  of  the  opposite  arch  w^hen  in  occlusion. 

4.  The  interproximal  space  at  the  median  line  above  and  below 
should  coincide.  ^Mien  they  do  not,  or  when  any  other  interproximal 
spaces  do  coincide,  a  malrelation  of  the  arches  is  present. 

5.  A  line  draTsm  vertically  through  the  median  axis  of  any  cuspid 
or  bicuspid  should  pass  between  the  antagonizing  teeth. 

6.  The  mesial  inclined  plane  of  any  cusp  occludes  against  the  distal 
inclined  plane  of  the  opposing  cusp ;  the  converse  therefore  is  likewise  true. 

7.  In  normal  occlusion  the  mesibbuccal  cusp  of  the  upper  first  molar 
occludes  between  the  mesiobuccal  and  buccal  cusps  of  the  lower  first 
molar. 

MALOCCLUSION 

Definition. — Any  deviation  of  the  teeth  or  arches  from  normal  rela- 
tion is  termed  malocclusion. 

Malocclusion  of  Individual  Teeth. — A  tooth  may  occupy  any  one 
of  seven  malpositions,  and  it  is  even  possible  for  it  to  be  malposed  in 
four  ways. 

These  malpositions  have  been  named  as  follows  (Angle) :  (1)  Labial 
or  buccal  occlusion.  (2)  Lingual  occlusion.  (3)  Mesial  occlusion. 
(4)  Distal  occlusion.  (5)  Supra-occlusion.  (6)  Infra-occlusion.  (7) 
Torso-occlusion. 

\.  Labial  or  buccal  occlusion  means  that  a  tooth  cro-v^oi  is  so  mal- 
posed that  it  is  labial  or  buccal  of  its  true  normal  position. 

2.  Lingual  occlusion  means  that  a  tooth  crown  is  so  malposed  that 
it  is  lingual  of  its  true  normal  position. 

3.  Mesial  occlusion  means  that  a  tooth  crown  is  mesial  of  the  posi- 
tion which  it  should  normally  occupy. 

4.  Distal  occlusion  means  that  a  tooth  crown  is  distal  of  the  position 
which  it  should  normally  occupy. 

5.  Supra-occlusion  means  that  a  tooth  has  erupted  to  an  abnormal 
height  in  its  socket. 


CLASSIFICATION  OF  MALOCCLUSION  245 

• 

6.  Infra-occlusion  means  that  a  tooth  has  not  erupted  to  a  normal 
height  in  its  socket. 

7.  Torso-occlusion  means  that  a  tooth  is  turned  in  its  socket  so  that 
it  does  not  occupy  its  normal  place  in  the  arch  alignment. 

In  explanation  of  the  statement  that  a  single  tooth  may  be  in  four 
positions  of  malocclusion  at  one  and  the  same  time,  I  would  cite  the 
following  example:  A  molar  tooth  may  be  in  torso-occlusion;  in 
buccal  or  lingual  occlusion;  in  mesial  or  distal  occlusion;  in  supra- 
or  infra-occlusion. 

Classification  of  Malocclusion.— It  is  manifest,  therefore,  that  there 
are  endless  varieties  of  malocclusion  when  viewed  in  the  light  of 
single  or  multiple  malpositions  of  the  individual  teeth.  It  remained 
for  Angle,  however,  to  discover  the  possibility  of  formulating  a  classi- 
fication for  malocclusion,  independent  of  these  individual  malpo- 
sitions but  based  upon  the  relations  of  the  two  arches  considered  as 
units.  Other  writers  have  endeavored  to  erect  classifications  which 
do  depend  upon  the  individual  malpositions,  but  in  none  of  these  is 
the  line  of  demarcation  between  the  described  classes  so  well  drawn 
that  it  may  serve  as  an  absolute  division  between  the  multiplicity  of 
conditions  that  arise.  The  result  is  that  often  cases  are  found  which 
might  fall  into  either  of  two  such  classes  or  even  into  both.  For 
example,  we  have  had  classes  for  "outstanding  cuspids" — cases  where 
the  cuspids  have  erupted  labially  of  normal.  Again,  classes  of  "open 
bite,"  meaning  an  infra-occlusion  or  lack  of  antagonization  of  the 
incisors.  What  are  we  to  do  then  with  a  case  where  we  have  "out- 
standing cuspids"  complicated  with  "open  bite?"  In  the  Angle 
classification  no  such  confusion  can  occur.  His  lines  of  demarcation 
are  so  distinct,  that  there  can  be  no  lapping  of  boundaries. 

Of  his  classification  Angle  writes:^  "These  classes  are  based  on  the 
mesiodistal  relations  of  the  teeth,  dental  arches,  and  jaws,  which  depend 
primarily  upon  the  positions  mesiodistally  assumed  by  the  first  per- 
manent molars  on  their  erupting  and  locking.  Hence,  in  diagnosing 
cases  of  malocclusion  we  must  consider  first,  the  mesiodistal  relations 
of  the  jaws  and  dental  arches,  as  indicated  by  the  relation  of  the  lower 
first  molars  with  the  upper  first  molars,  the  keys  to  occlusion;  and 
second,  the  position  of  the  individual  teeth,  carefully  noting  their 
relations  with  the  line  of  occlusion." 

Angle  then  has  divided  all  malocclusion  into  three  great  classes 
dependent  upon  the  mesiodistal  relations  of  the  arches  considered 
as  units.  It  is  evident,  then,  that  to  make  a  diagnosis,  we  must  always 
begin  with  a  picture  of  normal  molar  occlusion  in  the  mind,  and  with 
the  question,  "Is  the  mesiodistal  relation  of  the  molars  normal  on 
both  sides?"  The  answer  to  this  mental  question  will  invariably  clas- 
sify' the  case. 

1  Angle,  Seventh  edition,  p.  35. 


246  MALOCCLUSION  OF   THE   TEETH 

To  have  such  a  mental  picture  we  must  carefully  study  normal 
molar  relations,  as  shown  in  Fig.  98,  noting  that  the  mesiobuccal  cusp 
of  the  upper  first  molar  occludes  with  the  lower  first  molar  in  such  a 
way  that  a  line  drawn  through  the  apex  of  this  cusp  will  fall  directly 
into  the  buccal  groove  of  the  lower  molar.  Or  to  phrase  it  differently, 
the  mesiobuccal  cusp  of  the  upper  first  molar  occludes  between  the 
mesiobuccal  and  buccal  cusps  of  the  lower  first  molar,  whereas  the 
mesiobuccal  cusp  of  the  lower  first  molar  occludes  between  the  mesio- 
buccal cusp  of  the  upper  molar  and  the  buccal  cusp  of  the  upper 
second  bicuspid.  Thus  we  see  that  the  mesial  siu'face  of  the  lower  first 
molar  is  normally  slightly  mesial  to  the  corresponding  surface  of  the 
upper  first  molar.  Hence,  in  studying  mesial  occlusion  of  the  lower 
first  molar,  it  is  important  to  recognize  the  limitations  of  the  normal 
mesial  position  of  this  surface  in  relation  with  that  of  its  antagonists. 
When  the  cusps  are  not  mutilated  by  caries  or  bad  fillings,  how- 
ever, ^we  may  confine  ourselves  to  an  examination  of  the  cusp 
relations. 

The  Angle  Classification. — In  studying  a  case,  if  we  find  that  the 
mesiodistal  relations  of  the  upper  and  lower  first  molars  on  both  sides 
are  normal,  the  malocclusion  belongs  in  Class  I. 

If  the  lower  first  molar  on  one  or  both  sides  is  found  to  be  distal  to 
normal  in  relation  with  the  upper  first  molar,  it  is  said  to  be  in  distal 
occlusion,  and  the  malocclusion  falls  into  Class  II. 

If  the  lower  first  molar  on  one  or  both  sides  is  found  to  be  mesial  to 
normal  in  relation  with  the  upper  first  molar,  it  is  said  to  be  in  mesial 
occlusion,  and  the  malocclusion  falls  into  Class  HI. 

The  distinctions,  therefore,  between  Classes  I,  II,  and  III  are  very 
definite  and  should  be  readily  comprehended.  Some  confusion  has  been 
caused  in  the  minds  of  beginners  by  the  fact  that  there  are  divisions  and 
subdivisions,  but  these  likewise  may  be  so  plainly  described  that  there 
should  be  no  difficulty  whatever.  Once  having  learned  to  distinguish 
between  Classes  I,  II,  and  III,  we  next  learn  that  there  are  no  divi- 
sions in  Class  I  nor  in  Class  III.  But  Class  II  is  separated  into  two 
divisions:  Division  1,  wherein  the  upper  incisors  protrude,  and  Division 
2,  wherein  the  upper  incisors  retrude.  These  are  the  sole  factors  by 
which  the  divisions  of  Class  II  are  determined,  and  there  remains  no 
more  to  learn  except  the  subdivisions.  A  subdix'ision  is  any  case  of 
malocclusion  where  the  mesiodistal  relations  of  the  upper  and  lower 
first  molars  is  normal  on  one  side  and  abnormal  on  the  other.  If  the 
abnormality  be  a  distal  occlusion,  the  case  must  be  a  subdivision  of 
Class  II,  because  all  cases  of  distal  occlusion  are  in  Class  II.  If  the 
abnormality  be  a  mesial  occlusion  the  malocclusion  must  belong  to 
Class  III  because  all  mesial  occlusions  arc  in  Class  III. 

The  following  recapitulation  of  the  classification  is  copied  from  Angle, 
omitting  his  references  to  etiological  factors  with  which  we  are  not  at 
the  moment  interested: 


CLASSIFICATION  OF  MALOCCLUSION 


247 


Class  I.       Arches  in  normal  mesiodistal  relation. 
Class  11.     Lower  arch  distal  to  normal  in  its  relation  to  the  upper 
arch. 
Division  1.    Bilaterally  distal,  protruding  upper  incisors. 
Subdivimm.    Unilaterally  distal,  protruding  upper  incisors. 
Division  2.     Bilaterally  distal,  retruding  upper  incisors. 
Subdivision.    Unilaterally  distal,  retruding  upper  incisors. 
Class  III.    Lower  arch  mesial  to  normal  in  its  relation  to  the  upper 
arch. 
SiMivisioti.    Unilaterally  mesial. 
To  fix  the  differentiations  of  this  classification  more  firmly  in  the 
mind  let  us  examine  the  illustrations  of  a  few  typical  cases.    In  Fig. 
100,  an  examination  of  the  first  molars  discloses  that  on  each  side  the 
mesiodistal  occlusal  relations  are  normal.     On  each  side  the  mesio- 
buccal  cusp  of  the  upper  first  molar  occludes  between  the  cusps  of 


P'iG.  100. — Models  of  a  case  of  malocclusion,  Class  I. 


the  lower  first  molar,  and  a  line  drawn  through  the  central  axis  of  the 
mesiobuccal  cusp  of  the  upper  molar,  strikes  the  buccal  grove  of  the 
lower  first  molar.  This,  then,  discloses  a  bilateral  normal  mesiodistal 
occlusion  of  the  arches,  and  the  malocclusion  consequently  falls  into 
Class  I.  For  this  illustration  a  case  where  the  upper  incisors  protrude 
has  been  selected,  that  by  comparison  the  student  may  better  grasp 
the  difference  in  the  significance  of  protruding  incisors  in  Class  I  and 
Class  II,  Division  I. 

In  Fig.  100,  the  normal  mesiodistal  relations  of  the  first  molars  defin- 
itely fixes  the  case  in  Class  I.  Hence  the  protrusion  of  the  upper  incisors 
has  710  significance  in  connection  with  the  classification  of  the  case. 

In  Fig.  101,  an  examination  of  the  molars  shows  that  the  lower  molar 
on  each  side  is  in  distal  occlusion.  The  mesiobuccal  cusp  of  the  upper 
first  molar  does  not  coincide  with  the  buccal  groove  of  the  lower  first 
molar,  but  on  the  contrary  falls  between  the  mesiobuccal  cusp  of  the 
lower  molar  and  the  buccal  cusp  of  the  second  bicuspid.     The  case 


248 


MALOCCLUSION  OF   THE   TEETH 


therefore  falls  into  Class  II,  and  since  the  upper  incisors  protrude,  it  must 
be  in  the  first  dimsion  of  that  class.  Being  bilaterally  distal  with  the 
upper  incisors  protruding,  it  belongs  to  Class  II,  Division  1. 


Fig.  101. — Malocclusion:  Class  II,  Division  1. 

In  Fig.  102,  we  see  a  case  quite  like  the  last,  and  superficially  like 
Fig.  100,  but  a  study  of  the  molars  shows  a  distal  occlusion  on  one 
side  and  normal  mesiodistal  relations  on  the  other.  And  as  the  upper 
incisors  protrude,  it  is  placed  in  Class  II,  Division  1,  Subdivision. 

It  is  in  Class  II,  because  there  is  a  distal  occlusion;  it  is  in  Division 
1,  because  the  upper  incisors  protrude.  It  is  a  Subdivision  because  the 
distal  occlusion  is  confined  to  one  side.  It  is  therefore  unilaterally 
distal  with  protruding  upper  incisors. 


Fig.  102. — Malocclusion:  Class  II,  Division  1,  Subdivision. 


In  Fig.  lOij,  we  find  both  lower  first  molars  in  distal  occlusion.  The 
case  therefore  belongs  to  Class  II,  which  includes  all  distal  occlusions. 
We  note  that  the  upper  central  incisors  retrude,  for  which  reason  the 
case  belongs  to  Division  2.  It  is  therefore  a  case  belonging  to  Class  II, 
Division  2,  because  it  is  bilaterally  distal  with  upper  incisors  retruding. 


CLASSIFICATION  OF  MALOCCLUSION  249 

In  Fig.  104,  we  see  a  case  strikingly  like  the  last,  except  that  on  close 
examination  we  find  that  the  distal  occlusion  is  confined  to  one  side, 
for  which  reason  it  must  be  a  subdivision  case.  It  belongs,  therefore, 
to  Class  II,  Division  2,  Subdivision,  being  unilaterally  distal  with 
retruding  upper  incisors. 


Fig.  103. — Malocclusion:  Class  II,  Division  2. 

In  Fig.  105,  we  find  the  lower  first  molars  mesial  to  normal.  Indeed, 
they  are  so  far  mesial  that  they  have  lost  all  occlusal  contact  with  the 
upper  first  molars,  so  that  the  classification  is  very  simple.  The  case 
must  belong  to  Class  III,  which  includes  all  mesial  occlusions.  An  ex- 
treme case  has  been  selected  for  this  illustration,  but  the  actual  normal 
mesiodistal  relations  must  always  be  in  the  mind  as  a  mental  picture 


Fig.  104. — Malocclusion:  Class  II,  Division  2,  Subdivision. 

with  which  the  case  in  hand  may  be  compared,  and  in  the  presence  of 
the  full  complement  of  permanent  teeth,  if  the  lower  molar  is  found 
to  be  mesial  to  normal,  the  case  belongs  to  Class  III. 

Observe,  however,  the  qualification  "in  the  presence  of  the  full  com- 
plement of  the  permanent  teeth."  The  premature  loss  of  a  temporary 
molar,  or  the  extraction  of  a  bicuspid  may  permit  a  lower  first  molar 


250  MALOCCLUSION  OF   THE   TEETH 

to  drift  abnormally  forward,  presenting  a  confusing  picture.  It  is 
always  to  be  remembered,  therefore,  that  this  entire  classification  is 
dependent  upon  the  presence,  or  space  for  the  eruption  of,  all  the  per- 
manent teeth,  and  the  drifting  of  teeth  due  to  extractions  or  loss  of 
temporary  teeth  is  always  a  matter  for  separate  consideration. 


Fig.  105. — Malocclusion:  Class  III. 

In  Fig.  106,  we  find  a  mesial  occlusion  on  one  side,  and  a  normal 
mesiodistal  relation  on  the  other,  for  which  reason  the  case  belongs 
to  Class  III,  subdivision. 

So  much  then  for  the  classification  or  diagnosis  of  cases  in  which 
the  first  permanent  molars  are  present.  It  is  more  than  likely,  how- 
ever, that  many  cases  will  be  seen  before  these  molars  are  erupted  or 


Fig.  106. — Malocclu.sion:  Class  III,  Subdivision. 

after  they  have  been  badly  mutilated  or  even  lost  through  the  ravages 
of  decay.  For  this  reason  it  is  well  to  note  that  the  occlusion  of 
the  second  deciduous  molars  closely  simulates  that  of  the  first  per- 
manent m(^lars  and  consequently  these  teeth  may  be  used  as  guides 
for  classification.     It  has  also  been  mentioned  that  the  permanent 


ETIOLOGY  OF  MALOCCLUSION  251 

cuspids  are  quite  staple  landmarks  and  are  useful  as  guides  to  the  occlu- 
sal conditions.  At  times  the  bicuspids  may  be  all  the  individual  has 
to  offer  from  which  to  classify  an  abnormality.  Hence  the  student 
can  clearly  see  that  an  intimate  knowledge  of  the  normal  relation  of 
every  tooth  is  absolutely  necessary  if  an  intelligent  grasp  of  the 
abnormal  is  to  be  expected. 

Etiology  of  Malocclusion. — One  might  write  at  great  length  upon 
the  etiology  of  malocclusion  without  at  all  exhausting  the  subject. 
In  this  particular  work  it  does  not  seem  essential  to  discuss  all  the 
theories  of  all  the  theorists.  The  aim  will  be  rather  to  disclose  those 
facts,  the  knowledge  of  which  will  enable  the  hygienist  to  fulfill  her 
avowed  purpose  of  calling  attention  to,  and  so  far  as  possible  abating, 
those  acts  or  causes  which  might  bring  about  or  aggravate  maloc- 
clusion. 

The  factors  involved  as  causative  agents  of  malocclusion  may  be 
divided  into  the  proved  and  the  unproved.  As  examples  of  the  un- 
proved theories  in  relation  to  the  causes  of  malocclusion,  enlargement 
of  the  tonsils,  nasal  obstruction,  mouth-breathing,  and  adenoids  may 
be  mentioned.  Whether  these  maladies  do  or  do  not  contribute  toward 
malocclusion,  they  are  evidences  of  a  reduced  vitality,  and  as  diseased 
conditions,  should  promptly  be  corrected. 

We  are  told  that  mouth-breathing  causes  malocclusions,  and  that 
adenoids  cause  mouth-breathing.  Conversely,  however,  certain  good 
rhinologists  hold  that  mouth-breathing  induces  adenoids,  due  to  the 
fact  that  the  inlialed  air,  normally  passing  through  the  nares  pro- 
duces a  tonic  effect  .upon  the  upper  pharynx,  whereas  when  taken 
through  the  mouth  and  thus  more  directly  into  the  lungs,  the  area 
usually  occupied  by  the  adenoid  vegetations  misses  this  tonicity  sup- 
plied by  the  air,  and  the  hypertrophies  are  induced.  An  ordinary 
rhinitis,  or  head  cold,  especially  during  early  infancy,  by  occluding 
the  nasal  air  passages,  forces  the  child  to  breath  through  the  mouth. 
If  the  rhinitis  be  long  neglected,  the  mouth-breathing,  which  begins 
as  a  temporary  necessity,  may  become  a  permanent  habit.  The  theory 
at  least  sounds  plausible  enough.  Consequently  a  hygienist  who 
notices  any  negligence  of  this  character,  where  her  charges  may  be 
suffering  with  a  head  cold  of  long  standing,  should  at  once  warn  the 
parent  or  guardians  of  the  possible  ill-results.  Far  better  would  it 
be  for  the  child  to  lose  a  few  days'  schooling  while  being  kept  in  bed  to 
cure  a  cold,  than  that  the  habit  of  mouth-breathing  should  become 
fixed. 

Among  the  proved  causes  of  malocclusion  we  may  enumerate: 

(a)  The  prematm'e  loss  of  deciduous  teeth. 

(6)  Extraction  of  permanent  teeth. 

(e)  Pernicious  habits,  and 

(fZ))^Lack  of  use. 

There  are  other  kno^\^l  causes  which  may  be  found  in  text-books, 
but  those  mentioned  are  of  special  interest  to  the  hygienist. 


252  MALOCCLUSION  OF   THE   TEETH 

(a)  The  Premature  Loss  of  Deciduous  Teeth. — The  loss  or  extraction 
of  a  deciduous  tooth,  especially  of  the  cuspids  or  any  one  of  the  buccal 
teeth,  will  almost  inevitably  produce  a  pernicious  effect  upon  the  per- 
manent teeth.  The  space  made  by  the  loss  of  the  temporary  tooth 
almost  invariably  closes,  in  part  or  entirely,  so  that  the  opening  needed 
for  the  oncoming  teeth  in  that  locality  is  reduced  in  proportion. 

Why  the  Space  Closes. — In  the  examination  of  a  three-year-old  arch, 
one  wonders  where  the  three  large  permanent  molars  will  find  space 
for  eruption.  This  space,  of  course,  must  be  provided  by  a  growth 
of  the  maxilla  and  mandible  distal  to  the  deciduous  teeth,  distal 
therefore  to  the  last  deciduous  molar.  This  growth  is  coincident  with 
(if  not  actually  caused  by)  the  development  and  eruption  of  the  per- 
manent molars.  The  result  is  a  forward  or  horizontal  movement  of 
the  whole  temporary  arch.  Let  us  study  it  in  detail.  To  make  room 
for  the  arriving  first  permanent  molar,  the  temporary  second  molar 
must  move  forward.  To  accomodate  this  movement  the  first  tempo- 
rary molar  must  move  forward,  and  so  on  around  the  arch,  each  tooth 
giving  way  as  the  tooth  behind  it  advances.  Let  us  suppose,  however, 
that  one  of  the  temporary  molars  has  been  lost.  A  space  is  thus  pro- 
duced so  that  the  first  permanent  molar  may  erupt  without  influenc- 
ing the  forward  movement  of  any  of  the  teeth  anterior  to  the  tooth 
extracted.  Lideed,  thi-ough  lip  pressure  the  space  may  even  allow  the 
anterior  teeth  to  be  forced  backward.  In  this  way,  by  closing  of 
the  space  while  the  underlying  bicuspid  is  yet  deep  in  the  bone,  the 
bicuspid  may  be  completely  shut  out  of  the  arch,  so  that  it  either 
remains  impacted,  or  else  must  erupt  buccally  or  lingually  of  normal. 

(6)  Extraction  of  Permanent  Teeth.- — -The  loss  of  any  permanent 
tooth  breaks  up  the  continuity  of  the  arch  and  destroys  the  occlusion. 
It  directly  effects  no  less  than  five  teeth.  The  two  adjacent  teeth 
losing  the  support  of  the  extracted  member,  are  often  forced  to  drift 
or  tip  toward  one  another.  This  tipping  and  drifting  is  more  likely 
to  be  extensive  when  the  extraction  occurs  prior  to  the  eruption  of 
the  second  molars,  as  the  eruption  of  these  distal  teeth  induces  a  dis- 
arrangement of  the  teeth  distal  to  such  spaces.  This  tipping  of  the 
teeth  interferes  with  the  normal  cusp  interdigitation  of  these  two  teeth 
with  the  three  antagonists  of  the  opposite  jaw.  Thus,  as  has  been 
said,  the  loss  of  one  permanent  tooth  may  directly  spoil  the  occlusion 
of  five  others.  Hence,  of  course,  all  permanent  teeth  which  can  be 
kept  in  a  state  of  health,  should  be  preserved  when  in  normal  position, 
and  when  out  of  position  should  be  brought  to  normal  occlusion,  if 
possible. 

(c)  Pernicious  Habits. — In  regard  to  habits,  perhaps  the  most  common 
is  sucking  the  thumb.  This  phrase,  "sucking  the  thumb,"  is  met 
throughout  the  entire  literature,  and  is  particularly  supposed  to  induce 
protrusion  of  the  upper  anterior  teeth.  But  the  thumb  is  not  always 
in  the  mouth  in  such  a  way  as  to  produce  this  effect,  nor  is  it  always 
the  thumb  which  the  child  introduces  into  the  mouth.    Recently  a 


THE  GROWTH  OF  THE  JAWS  253 

casual  glance  into  the  mouth  of  a  baby  girl  patient  of  four,  disclosed 
what  seemed  to  be  a  protrusion  of  the  upper  incisors.  The  mother 
was  asked,  "Does  this  child  suck  her  thumb?"  Like  a  flash  the  child 
replied,  "No,  I  suck  two  fingers;  want  to  see  me?"  and  she  proceeded 
to  give  a  demorstration.  She  placed  just  two  fingers  of  her  right 
hand  in  her  mouth,  the  finger-tips  curled  downward  under  her  tongue. 
In  this  manner  it  would  seem  that  the  weight  of  her  arm  had  held 
the  mandible  downward  and  backward,  so  that  a  marked  example  of 
Class  II,  Division  1,  had  been  produced,  although  none  of  the  tem- 
porary teeth  had  yet  been  shed.  The  apparent  protrusion  of  the 
upper  teeth  was  no  real  protrusion  at  all.  As  the  child  was  not  a 
sufferer  from  adenoids,  had  no  nasal  obstruction  of  any  sort,  had 
never  been  a  mouth-breather,  and  was  the  picture  of  health,  it  is  rea- 
sonable to  attribute  the  deformity  of  the  jaws  in  her  case  to  this 
peculiar  method  of  sucking  the  fingers.  The  thumb  is  also  sometimes 
introduced  into  the  mouth  in  the  same  manner,  and  not  always  with 
the  ball  of  the  thumb  against  the  upper  teeth. 

Other  baneful  habits  are  sucking  the  lips  or  the  tongue,  or  habit- 
ually resting  the  tongue  between  the  incisors,  not  forgetting  the  abom- 
inable practice  of  nursemaids,  and  some  mothers,  of  giving  the  baby 
a  "pacifier"  or  "comforter." 

These  habits  are  particularly  mentioned  here  because  it  seems  prob- 
able that  in  the  near  future  the  sphere  of  the  dental  hygienist  will  be  so 
broadened  that  she  will  enter  the  homes  of  many  children  long  before 
they  arrive  at  the  school  age,  in  which  case  an  important  part  of  her 
duty  would  be  to  look  for,  and  warn  mothers  against,  these  habits. 

(c/)  Lack  of  Use. — This  brings  us  to  a  consideration  of  a  lack  of 
use.  It  is  a  commonly  accepted  physiological  law  that  the  use  of  any 
organ,  or  part  of  the  body,  contributes  toward  its  development.  Nor- 
mal use  results  in  normal  development,  where  not  hindered  by  other 
agencies.  Abnormal  or  immoderate  use  may  cause  an  overgrowth, 
as  we  see  in  the  muscles  of  athletes;  while  disuse  results  in  under- 
development or  even  atrophy. 

The  Growth  of  the  Jaws. — If  we  examine  the  normal  child  denture 
at  the  age  of  three  or  four,  we  observe  twenty  teeth  symmetrically 
arranged  about  the  arches  and  completely  filling  them.  When  we 
remember  that  these  twenty  deciduous  teeth  will  be  succeeded  by 
twenty  permanent  teeth  considerably  larger  in  size,  we  recognize  that 
if  the  latter  are  to  erupt  in  normal  occlusion,  the  bones  of  the  arches 
must  become  enlarged,  or  in  other  words,  there  must  be  a  growth 
increasing  the  circumference  of  the  arches.  Since  the  growth  of  the 
temporary  teeth  themselves  is  already  complete,  a  growi:h  of  their 
bony  supports  must  result  in  producing  spaces  between  these  teeth. 
We  see  this  beautifully  shown  in  Fig.  107,  which  illustrates  the  upper 
and  lower  arches  of  a  boy  of  four  and  a  half  years  of  age.  We  have  but 
to  glance  at  such  a  set  of  deciduous  teeth  to  see  how  admirably  Nature, 
when  unhmdered,  will  provide  for  all  emergencies.    We  easily  compre- 


254  MALOCCLUSION  OF  THE  TEETH 

hend  that,  by  growth,  space  is  being  provided  against  the  advent  of  a 
set  of  larger  teeth. 

But  what  shall  we  think  of  such  a  set  of  teeth  as  is  shown  in  Fig. 
108  ?  This  child  was  five  years  of  age,  six  months  the  senior  of  the  other 
child,  yet  we  find  no  spaces  between  the  teeth  and  consequently  no 
growth  of  the  alveolar  bone.  We  must  wonder  then,  "Where  will 
the  permanent  teeth  erupt?"    They  certainly  cannot  appear  in  proper 


Fig.  107. — Normal  growth  of  dental  arches.     Age  ^\  years. 

alignment  with  such  a  lack  of  space.  These  two  models  then,  illustrate 
well  the  contrast  in  appearance  of  a  normally  developing  deciduous 
denture  with  one  that  is  failing  to  take  on  proper  growth. 

It  is  but  natural  to  believe  that  this  development  of  the  bones  about 
the  deciduous  teeth  is  largely  dependent  upon  the  extent  and  nature 
of  the  use  or  disuse  of  the  teeth. 

The  normal  use  of  the  teeth  would  necessitate  the  thorough  masti- 
cation of  food;  food  thus  masticated  would  be  properly  insalivated. 


Fig.  108.^Uridcveloped  dental  arches.     Age  .5  years. 

and  hence  projjcrly  j)rcparcd  for  its  reception  })y  the  stomach.  With 
all  the  organs  of  digestion  in  a  state  of  health,  the  result  would  be  the 
thorough  assimilation  of  the  food,  a  correct  metabolism,  and  hence 
a  pr(^pcr  share  of  the  nourishment  would  finally  reach  the  jaw-bones, 
so  that  the  thoroughness  of  the  work  done  by  the  (leiital  organs  would 
bring  its  own  repayment  in  the  normal  share  of  ymbulum  brought  to 
the  alveolar  environments  of  the  teeth.     In  this  manner  a  normal 


MASTICATION  IN  RELATION  TO  DEVELOPMENT  255 

physiological  cycle  would  he  established,  and  of  course  any  disuse  of 
the  teeth  would  proportionately  cause  a  disarrangement  of  this  cycle. 

While  it  is  well  to  bear  these  facts  in  mind,  yet  there  is  another  aspect 
of  use  and  disuse  of  the  dental  organs  to  which  attention  must  here 
be  called.  Entirely  aside  from  any  interference  with  the  proper  nour- 
ishing of  the  body  and  of  the  jaw-bones,  the  use  or  disuse  of  the  teeth 
directly  affects  the  growth  and  development  of  the  maxilla  and  man- 
dible, through  the  muscular  and  mechanical  forces  of  mastication. 
Indeed  it  is  claimed  that  not  only  the  bones  of  the  jaws,  but  the  entire 
cranium  may  be  thus  affected.  To  emphasize  this  fact,  a  liberal  quo- 
tation is  made  from  an  article  by  Dr.  Lawrence  W.  Baker,  published 
in  Items  of  Interest,  February,  1911. 

"Among  the  first  voluntary  coordinate  muscular  actions  of  a  human 
being  after  coming  into  the  world  is  that  made  with  the  muscles  of 
mastication  in  taking  food  to  sustain  life.  Long  before  the  infant 
can  hold  up  its  head,  or  has  gained  control  over  those  useful  organs, 
the  hands,  the  muscles  of  mastication  are  highly  developed  and  are 
used  with  great  vigor. 

"During  the  act  of  nursing,  the  action  of  this  set  of  muscles  is  so 
vigorous  that  it  demands  an  increased  blood  supply,  to  the  extent  that 
the  heart's  action  is  greatly  increased;  the  excessive  flow  of  blood  to 
these  parts  is  indicated  by  a  reddening  of  the  whole  head,  and  the  fon- 
tanelles  themselves  are  caused  to  pulsate  so  that  the  untrained  obser- 
vers comment  on  their  movement. 

"Later,  with  the  advent  of  the  dental  equipment,  this  group  of 
muscles  is  given  more  leverage,  and  its  action  becomes  consequently 
more  powerful;  in  fact,  the  force  exerted  on  the  bones  of  the  head 
from  the  pull  of  these  muscles  during  life  is  tremendous  and  amounts 
to  many  hundreds  of  thousands  of  tons  of  force.  I  have  long  been 
convinced  that  this  great  force  on  the  skull,  and  the  great  flow  of  arte- 
rial blood  to  the  head  caused  by  this  muscular  activity,  is  a  powerful 
influence  in  the  de\'elopment  of  the  bones  of  the  head  and  the  impor- 
tant organs  incased  therein. 

"It  occurred  to  me  that  if  the  hypothesis  regarding  the  influence 
of  the  dental  equipment  on  the  formation  of  the  bones  of  the  head  were 
correct,  interference  with  the  laws  of  occlusion  in  the  lower  animals 
would  show  consequent  effect  in  the  formation  of  the  bones  of  the 
skull ;  and  if  variation  occurred  it  might  throw  some  light  on  the  most 
complex  problem  of  the  development  of  the  human  head. 

"To  test  the  theorj^  the  following  experiment  was  performed:  A 
litter  of  four  rabbits  was  selected  at  the  age  of  weaning.  Two  of  the 
animals  were  operated  on  by  grinding  do^vm  all  the  teeth  on  the  right 
side  of  the  lower  jaw  and  the  superior  right  central  incisor.  As  the 
teeth  elongated,  repeated  grinding  rendered  them  useless,  so  that 
all  the  mastication  was  performed  on  the  left  side.  The  fourth  rabbit 
was  kept  in  the  normal  state  for  a  standard  of  comparison. 

"  After  seven  months,  the  skeleton  of  one  of  the  rabbits  was  procured 


256 


MALOCCLUSION  OF   THE   TEETH 


and  the  skull  was  found  to  vary  as  is  sho\\ni  in  Fig.  109,  which  is  a  photo- 
graph of  its  upper  aspect.  It  will  be  noted  by  the  dra-^ai  lines  that 
there  is  a  deviation  of  the  bones  to  the  left.  (Right  and  left  in  this 
description  refers  to  the  right  and  left  side  of  the  animal).  The  suture 
between  the  parietal  and  frontal  bones  does  not  run  strictly  at  right 
angles  to  the  longitudinal  axis  of  the  skull;  the  right  frontal  bone 
projects  farther  forward  than  the  left  one.  It  will  also  be  observed 
that  the  left  zygomatic  space  is  longer  and  more  advanced  than  the 
right  space.  The  most  noticeable  deviation  is  in  the  nasal  bones, 
both  bones  being  twisted  to  the  left. 


Fig.  109. — The  upper  aspect  of  the 
skull  of  a  rabbit  operated  on.  Obser%'e 
the  unequal  development  of  each 
lateral  half  of  the  skull. 


Fig.  110.— Lower  aspect  of  Fig.  109. 


"On  the  lower  aspect  of  the  skull.  Fig.  110,  it  will  be  seen  that  the 
deviation  extends  throughout  the  entire  skull.  The  most  remarkable 
deviation  is  that  the  anterior  root  of  the  right  zygomatic  arch  (the 
zygomatic  process  of  the  maxillary  bone)  is  retreated  while  the  body 
of  the  right  maxillary  bone  itself  with  the  teeth  that  it  contained  is 
greatly  advanced. 

"The  results  of  this  ex-periment  seem  remarkable  to  me. 

"Who  would  have  thought  that  by  interfering  with  the  laws  of 
occlusion  the  skull  would  have  decreased  in  weight,  and  that  every 
suture  and  every  bone  in  the  head  would  have  varied  as  we  have  seen? 
This  experiment  strongly  indicates  how  important  is  the  masticatory 


CAUSES  OF  IMPAIRED  FUNCTION 


Zo< 


equipment  of  man  to  the  development  of  the  head,  and  it  also  brings 
fresh  illustrations  of  the  importance  of  the  sadly  neglected  temporary 
dentition  which  serves  during  the  important  developmental  period 
of  childhood." 

The  previous  quotation  gives  in  full  the  details  of  Dr.  Baker's 
experiment,  and  his  findings  in  one  case.  His  examination  of  the 
second  rabbit  upon  which  he  experimented  disclosed  exactly  similar 
variations  from  the  normal,  whereas  the  control  animal  was  practically 
symmetrical.^  Until  future  experimenters  prove  these  deductions  to 
be  erroneous,  we  may  agree  with  Dr.  Baker  that  the  disuse  of  the 
teeth  may  result  in  extreme  interference  with  the  development,  not 
alone  of  the  jaws,  but  of  contiguous  parts  of  the  cranium. 

Reasons  for  Lack  of  Use. — Disuse  of  the  dental  organs  may  be  either 
involuntary  or  \oluntary.  It  is  involuntary  when  the  habits  of  masti- 
cation are  hastv,  or  where  the  food  used  is  of  such  a  character  that 


Fig.  111. — Caries  of  teeth  causing  voluntary  disuse  of  the  teeth. 


heavy  mastication  is  not  necessary.  What  an  injustice,  then,  is  done  to 
children  who  are  fed  upon  gruels,  sloppy  food  and  other  articles  of 
diet  which  require  little  or  no  masticatory  effort  to  reduce  them  to  a 
consistency  readily  swallowed? 

The  voluntary  disuse  of  the  teeth  is  the  direct  result  of  caries  which 
renders  the  chewing  of  food  so  difficult,  or  so  painful,  that  the  child 
elects  either  to  swallow  its  food  unchewed,  or  else  to  select  food  that 
needs  no  masticatory  effort. 

In  Fig.  Ill,  we  see  the  right  and  left  sides  of  the  occluded  models  of 
a  child  four  years  of  age.  On  the  left  side  of  the  mouth  caries  has 
destroyed  the  little  molars  and  cuspids  almost  to  the  gum  line.  We 
cannot  look  upon  this  picture  without  thinking  of  the  rabbits,  whose 

1  Dr.  Baker  has  continued  his  experiments,  and  has  had  exactly  similar  results  with 
animals  other  than  rabbits.  See  his  report  thereon,  Dental  Items  of  Interest,  July, 
1916. 

17 


258  MALOCCLUSION  OF   THE   TEETH 

teeth  Dr.  Baker  filed  or  ground  away  to  prevent  mastication  on  one 
side.  When  we  recall  the  results  of  the  experiment  with  the  rabbits, 
we  begin  to  appreciate  the  seriousness  of  such  conditions  in  a  human 
young  one,  during  the  most  stressful  periods  of  development.  The  word 
stressful  is  used  because,  whereas  an  adult  needs  only  to  restore  the 
tissues  of  his  body  which  are  lost  by  use,  a  child  must  likewise  do  this 
and  at  the  same  time  obtain  and  assimilate  sufficient  food  with  which 
to  increase  his  weight  and  stature.  How  can  he  do  this  handicapped 
with  a  masticating  apparatus  so  destroyed  ?  In  the  experiment  with 
the  rabbit,  Dr.  Baker  left  the  little  animal  one  side  of  his  masticating 
apparatus  perfect,  so  that  perhaps  he  might  properly  masticate  suffi- 
cient food  for  the  proper  noiu^ishment  of  his  body.  It  is  this  fact  that 
made  Dr.  Baker's  results  so  significant.  There  is  every  reason  to  believe 
that  the  rabbits  operated  upon  ate  just  as  much  food  as  the  control 
animal,  so  that  the  divergencies  from  normal  found  in  the  skulls  were 
not  attributable  to  lack  of  nourishment,  but  to  lack  of  use  of  one  side 
of  the  jaws. 


Fig.  112. — Same  case  as  Fig.  Ill,  occlusal  view. 

The  child  whose  models  are  shown  fared  not  so  well  as  Dr.  Baker's 
rabbits,  because  on  both  sides  occlusion  was  extensively  interfered 
with.  The  cavities  in  the  teeth  are  so  large  that  a  considerable  por- 
tion of  their  occlusal  areas  have  been  lost,  and  the  approximal  con- 
tacts likewise  having  been  destroyed,  the  protection  of  the  interprox- 
imal septa  has  disappeared,  so  that  food  readily  packs  upon  these 
easily  injured  and  sensitive  tissues,  with  the  result  that  mastication 
becomes  painful,  and  the  child  voluntary  declines  to  use  his  teeth. 

Fig.  112,  shows  the  occlusal  view  of  these  two  jaws,  and  the  extent 
to  which  caries  has  destroyed  the  occlusal  contactual  area  is  disclosed. 
Comparing  these  models  with  those  shown  in  Fig.  107,  we  note  the 
lack  of  development. 

At  this  point  it  may  be  well  to  consider  again  the  models  shown  in 
Fig.  108.  These  likewise  show  lack  of  development  of  the  arches,  yet 
the  teeth  themselves  are  not  affected  by  caries,  so  the  child  could 
have  used  them  perfectly;  therefore  it  is  not  to  be  claimed  that  disuse 
is  the  sole  cause  of  lack  of  development.    It  may  be  the  chief  cause 


THE  RESULT  OF  IMPAIRED  FUNCTION 


259 


in  some  instances  and  only  one  of  several  factors  in  others.  In  the 
case  of  the  child  whose  models  are  shown  in  Fig.  108,  the  physical  his- 
tory is  not  known.  It  will  suffice  for  present  purposes  to  consider  two 
possible  hypotheses.  While  this  child  cannot  have  suffered  from  vol- 
untary disuse  of  the  dental  organs,  since  the  teeth  are  all  sound,  there 
may  have  been  involuntary  disuse  due  to  the  soft  nature  of  his  food. 


Fig.  113. — Malocclusion  due  to  lack  of  use. 

Again,  considering  the  perfectness  of  the  teeth,  this  may  not  be  a  case 
of  lack  of  development  at  all.  There  is  no  definite  age  at  which  a 
particular  development  of  the  jaws  must  occur.  We  cannot  say  cer- 
tainly that  the  first  permanent  molars  will  erupt  at  a  stated  age,  the 
incisors  at  another,  the  cuspids  at  another.  The  writer  has  seen  a 
complete  denture  of  thirty-two  teeth  at  the  age  of  fourteen,  and  in 


Fig.  114. — Same  case  as  Fig.  113,  occlusal  view. 


another  case,  the  upper  cuspids  arriving  as  late  as  the  nineteenth  year, 
in  which  case  all  the  previously  erupted  teeth  had  likewise  appeared 
long  after  what  is  supposed  to  be  the  normal  time  of  eruption.  Look- 
ing at  a  child  denture  prior  to  the  eruption  of  the  first  permanent 
molars,  if  we  note  growth  spaces,  as  seen  in  Fig.  107,  we  may  say  that 
normal  development  is  present,  but  in  the  absence  of  such  growth 


260  MALOCCLUSION  OF   THE   TEETH 

spaces,  as  in  Fig.  108,  we  cannot  positively  decide.  It  may  be  a  case 
of  lack  of  development  (as  a  mere  illustration  of  which  the  models 
are  used),  or  it  may  be  a  case  of  slow  or  tardy  development. 

As  examples  of  a  period  slightly  later  than  that  shown  in  Figs.  Ill 
and  112,  P'igs.  113  and  114  are  introduced.  This  child's  mouth  was 
first  examined  prior  to  the  appearance  of  the  permanent  molars.  Not 
a  tooth  in  the  two  arches  was  free  from  caries.  .The  upper  incisors  were 
barely  showing  above  the  gum  line,  and  all  four  were  abscessed,  for 
which  reason  they  were  extracted,  as  were  three  or  four  others.  Com- 
.plete  lack  of  occlusion  existed.  The  child  was  undersized,  anemic,  and 
of  a  generally  degenerate  appearance.  Her  father  was  a  physician, 
however,  and  after  removal  of  the  abscessed  teeth  he  was  advised  to 
feed  the  child  on  food  that  would  yield  as  much  nourishment  as  possible. 
It  was  impossible  to  obtain  models  of  her  mouth;  it  would  have  been 
cruel  to  try.  When  next  she  was  seen,  two  years  later,  the  models  here 
illustrated  were  made.  Even  with  the  eruption  of  the  first  molars, 
the  masticating  possibilities  have  not  been  greatly  improved,  as  they 
decayed  almost  as  fast  as  they  appeared,  so  it  was  said.  However 
that  may  be,  we  have  here  a  marked  case  of  prolonged  lack  of  use  and 
malnutrition  and  cannot  be  surprised  at  the  resultant  malocclusion. 
On  one  side  we  note  that  the  lower  molar  is  in  distal  occlusion.  On 
the  other  side  the  occlusion  of  the  molars  is  apparently  normal,  but 
there  is  little  reason  to  doubt  that  the  lower  molar  has  drifted  forward 
because  of  the  premature  loss  of  the  two  temporary  teeth.  In  any 
event  it  is  a  marked  example  of  malocclusion  due  to  lack  of  use  follow- 
ing the  ravages  of  caries  in  the  temporary  set,  so  that  from  this  case 
alone  we  may  gain  some  cognizance  of  the  possible  evils  of  dental 
disease  which  might  have  been  prevented  to  a  great  degree  by  proper 
attention  to  mouth  hygiene. 


CHAPTER  X. 
PYORRHEA  ALVEOLARIS 

By  R.  G.  HUTCHINSON,  Jr.,  D.D.S. 

Strictly  speaking,  the  term  pyorrhea  alveolaris  can  l)e  apphed 
only  to  conditions  in  which  there  is  an  exhibition  of  pus.  As  this 
is  the  case  in  but  a  percentage  of  the  pathological  ])rocesses  which 
destroy  the  tissues  supporting  the  teeth,  it  is  a  most  inadequate  and 
inappropriate  term  to  use  as  descriptive  of  such  conditions  in  general. 
Common  usage  often  brings  about  the  acceptance  of  terms  or  words 
improperly  applied,  and  as  the  profession  has  almost  universally 
employed  the  name  pyorrhea  alveolaris  in  speaking  of  infections  affect- 
ing the  peridental  membrane  and  alveolar  process,  together  with  the 
overlying  soft  tissues,  we  are  therefore  justified  in  accepting  such 
application. 

As  the  general  causes  leading  to  infection,  the  ultimate  results  of 
such  infection,  and  the  treatment  are  substantially  the  same  in  all 
cases,  they  will  be  considered  collectively. 

Etiology. — Every  mouth  contains  many  different  forms  of  bacteria, 
pathogenic  and  otherwise.  The  mouth,  with  its  temperature,  moisture, 
and  abundance  of  culture  medium,  is  an  ideal  incubator.  Cultures 
are  therefore  easily  established.  Normally,  the  tissues  offer  sufficient 
resistance  to  prevent  destruction,  unless  an  extremely  unsanitary 
condition  is  permitted  to  exist.  As  the  establishment  of  a  destructive 
infection  must  result  from  the  overcoming  of  resistance  by  attack, 
attention  must  be  directed  to  the  cause  of  lowered  resistance  as  well 
as  the  direct  cause  of  infection. 

Clinical  observation  has  shown  that  in  the  great  majority  of  cases 
the  infection  exists  at  some  point  of  injury.  In  other  words,  trauma 
is  frequently  the  starting-point  of  pyorrhea  alveolaris.  The  tissues 
having  been  injured,  inflammation  results,  the  active  organisms  which 
are  present  establish  a  focus  and  the  destruction  begins. 

There  are  some  cases,  however,  in  which  there  is  no  appreciable 
traumatic  condition.  Such  cases  are  due  to  general  low  resistance  to 
the  particular  form  of  organism  which  establishes  itself. 

The  conclusion  must  therefore  be  that  pyorrhea  alveolaris  is  caused 
by  an  infection  of  tissue  whose  resistance  has  been  reduced,  either  by 
traumatic  influence,  or  on  account  of  some  systemic  factor. 

It  must  always  be  borne  in  mind  that  the  presence  of  bacteria  is 
necessary,  and  pyorrhea  alveolaris  cannot  exist  without  them.    When 


262  PYORRHEA  ALV SOLARIS 

the  tissues  are  uninjured  and  high  resistance  exists,  no  harm  will  be 
done  by  their  presence,  but  when  the  attacking  force  is  stronger  than 
the  defense,  a  pathological  condition  is  the  result. 

Therefore  the  matter  may  be  summed  up  in  this  way:  The  causes 
of  pyorrhea  ah-eolaris  are  positive,  active  or  direct;  and  negative, 
passive  or  indirect.  The  former  are  local  and  the  latter  constitu- 
tional. 

Even  with  a  very  high  constitutional  resistance,  such  resistance  may 
be  overcome  by  injury,  and  infection  may  occur.  It  is  all  a  matter 
of  the  relative  strength  of  attack  and  defense.  Pyorrhea  alveolaris  is 
not,  as  has  often  been  said,  "A  local  expression  of  a  systemic  dis- 
order." If  a  systemic  disorder  which  affects  nutrition  or  elimination 
exists,  of  course  a  local  lesion  is  more  easily  established,  and  its 
progress  will  be  more  rapid  and  destructive. 

Whatever  strengthens  the  attack  or  weakens  the  defense,  facilitates 
the  establishment  and  progress  of  the  local  disease;  and  whatever 
weakens  the  attack  or  strengthens  the  defense,  is  unfavorable  to  the 
local  pathological  condition. 

Causes. — The  most  common  cause  of  pyorrhea  alveolaris  is  mal- 
occlusion. The  improper  apposition  of  the  occlusal  surfaces  results  in 
a  venous  hyperemia  of  the  peridental  membrane,  so  lowering  resist- 
ance. x41so  through  malocclusion,  the  teeth  are  not  performing  normal 
function,  and  the  tissues  surrounding  them  suffer  from  malnutrition. 
When  the  teeth  are  crowded,  the  alveolar  septum  is  thin  and  less 
resistant  to  attack,  and  it  is  always  more  difficult  to  maintain  san- 
itation. 

Some  of  the  other  local  exciting  causes  are  faulty  dental  operations, 
such  as  ill-fitting  crowns  and  bridges  which  not  only  lacerate  the  tissues 
but  accumulate  food  debris  which  the  patient  cannot  remove;  fillings 
impinging  on  the  gum  margins;  fillings  improperly  contoured,  allow- 
ing impaction  of  food  in  the  interproximal  space;  septic  teeth;  improper 
application  of  rubber  dam  and  clamps;  rapid  or  excessive  separation 
of  teeth;  laceration  of  tissues  in  finishing  fillings;  injury  by  improper 
instrumentation,  for  the  removal  of  tartar,  etc.  In  short,  anything 
which  establishes  trauma,  invites  pyorrhea  alveolaris. 

As  before  stated,  the  systemic  factors  are  passive  or  negative,  and 
may  be  inherent  or  acquired.  Some  individuals  possess  to  a  high  degree 
the  ability  to  repair  tissue  which  has  been  injured  and  to  resist  injury, 
or  to  resist  many  forms  of  infection,  and  others  do  not.  This  is  an 
inherent  factor. 

Where  such  systemic  diseases  as  tuberculosis,  diabetes,  Bright's 
disease  or  syphilis  occur,  pyorrhea  alveolaris  may  be  present  in  an 
aggravated  form  on  account  of  low  resistance,  but  almost  invariably 
the  inception  of  the  pyorrhea  antedates  the  establishment  of  the  sys- 
tcniif:  disease. 

Progress  of  Disease. — Pyorrhea  alveolaris  begins  with  an  inflamma- 
tion either  at  the  point  of  injury  or  at  the  gingival  margins,  especially 


TREATMENT  263 

in  the  interproximal  space.  The  inflammation  results  in  the  formation 
of  deposits  of  serumal  calculus,  which  })ecomes  what  may  be  called  a 
secondary  exciting  cause.  In  some  cases  pus  is  formed,  and  in  others 
destruction  of  the  tissues  takes  place  without  pus  being  present.  This 
destruction  will  continue  until  the  teeth  are  lost,  unless  correct  treat- 
ment is  given. 

Symptoms. — The  symptoms  vary  according  to  the  existing  condi- 
tions and  the  stage  of  progress.  In  its  inception,  slight  redness  of  the 
gingiva  presents,  sometimes  w'ith  more  or  less  serumal  deposits.  In 
more  advanced  stages,  the  gums  wull  be  highly  congested,  pus  flowing 
profusely  and  teeth  loosened. 

There  are  many  cases,  the  existence  of  which  can  be  determined  only 
by  careful  thorough  exploration  under  the  gum  margins.  Where  much 
tissue  has  been  lost,  or  deposits  on  the  necks  or  roots  of  the  teeth  are 
present,  there  is  no  diflSculty  in  determining  the  presence  of  a  patholog- 
ical condition. 

Treatment. — The  first  step  in  the  treatment  of  any  case  of  pyorrhea 
alveolaris  should  be  to  determine  w^here  excessive  stress  exists  in 
occluding  the  teeth,  both  at  rest  and  in  every  possible  position  to  be 
assumed  by  the  jaw.  All  cusps  must  be  properly  ground  and  points 
of  contact  established  in  such  a  way  that  the  stress  will  be  equally 
distributed  in  all  positions. 

All  faulty  dental  operations  should  be  corrected. 

Septic  teeth  must  be  sterilized  or  removed.  The  sooner  this  is  done, 
the  bettc'r  the  result  of  instrumentation  will  be. 

It  must  be  remembered  that  not  only  must  health  be  restored,  but 
function  must  be  established,  and  finally,  sanitation  maintained. 
Any  tooth  which  cannot  be  kept  in  a  sanitary  condition  by  the  patient, 
should  be  removed.  A  sanitary  artificial  substitute  is  always  prefer- 
able to  an  unsanitary  natural  organ. 

All  deposits  of  calculus  must  be  removed  and  surfaces  of  roots  deli- 
cately curetted  for  the  removal  of  necrotic  membrane,  and  finally, 
the  teeth  must  be  polished  perfectly. 

In  treating  pyorrhea  alveolaris,  every  factor  which  tends  to  injure 
the  tissues  or  cause  infection  must  be  considered  and  properly  removed, 
or  failure  is  inevitable. 

The  operator  removes  that  which  nature  cannot  overcome,  but 
nature  heals  and  builds  up  the  tissues.  Therefore  nothing  harmful 
must  be  left  and  nothing  must  be  done  to  interfere  with  that  reparative 
process  which  must  take  place  in  order  to  eft'ect  a  cure. 

Practically  no  systemic  condition  which  does  not  prostrate  a  patient 
will  prevent  successful  treatment,  and  most  systemic  factors  can  be 
ignored  in  the  treatment,  except  that  more  delicacy  and  care  must 
be  exercised  where  general  low  resistance  exists.  Failure  is  often  due 
to  excessive  injury  attending  unskilful  instrumentation  and  is  fre- 
quently followed  by  a  secondary  infection  more  serious  than  the 
original. 


264  PYORRHEA   ALV SOLARIS 

Postoperative  Treatment. — After  the  disease  has  been  eliminated  and 
health  restored,  it  must  be  maintained.  This  is  accomplished  mainly 
through  sanitary  measures,  both  by  the  patient  and  the  operator. 
The  intervals  between  prophylactic  treatments  must  be  determined 
in  each  individual  case. 

Prophylaxis  means  prevention  of  disease,  therefore  the  cleaning 
of  the  teeth  by  the  operator  must  be  done  before  recurrent  inflamma- 
tion is  established. 

The  fact  that  prophylactic  treatment  is  necessary  in  order  to  main- 
tain health  in  the  oral  cavity  in  no  way  proves  that  the  disease  is  not 
cured,  but  on  the  contrary,  proves  the  local  origin  of  pyorrhea  alveo- 
laris.  Even  where  systemic  predisposing  factors  exist,  pyorrhea 
alveolaris  either  primary  or  recurrent,  can  be  prevented  by  local 
measures  alone. 

The  point  at  which  resistance  is  overcome  varies  in  different  cases. 

Medication. — Medication,  either  local  or  constitutional,  is  practically 
useless  as  a  curative  factor.  Foreign  irritants  and  pathological  tissue 
must  be  surgically  removed,  and  causative  factors  eliminated.  The 
only  effective  use  of  medicaments  consists  of  the  application  of  such 
materials  as  will  tend  to  prevent  recurrent  infection  and  act  as  pallia- 
tives. Whatever  is  antagonistic  to  bacterial  growth,  without  irritation 
or  destruction  of  the  tissues,  is  conducive  to  the  establishment  and 
maintenance  of  health.  A  healthy  mouth  can  neither  be  established  nor 
maintained,  but  by  depriving  the  bacteria  as  perfectly  as  possible 
of  culture  medium,  we  lessen  the  number  by  a  starvation  process. 
The  use  of  mild  antiseptics  inhibits  bacterial  growth  in  food  deposits 
which  the  patient  cannot  remove,  and  reduces  the  virulence  of  the 
bacteria  present. 

Vaccine  Treatment. — The  use  of  vaccines  is  not  only  unnecessary 
but  detrimental,  as  such  treatment  merely  makes  possible  the  continued 
existence  of  mechanical  irritants,  bacteria,  and  pathological  tissue  with- 
out the  exhibition  of  superficial  symptoms.  Such  masking  of  symp- 
toms misleads  the  operator  into  believing  that  a  cure  has  been  effected 
when  such  is  not  the  case.  If  the  proper  surgical  treatment  has  been 
given,  in  every  detail,  and  the  patient  faithfully  carries  out  proper 
instructions,  nature  will  rapidly  repair  the  damaged  tissues  without 
any  other  assistance.  This  applies  in  a  general  way  to  powerful  germi- 
cides and  astringents  applied  locally.  They  give  only  temporary 
relief,  and  are  liable  to  ultimately  cause  increased  destruction  of  tissue. 

The  only  logical  method  of  treatment  of  accessible  infections  is  to 
remove  direct  causes,  and  not  to  establish  an  artificial  resistance 
wliic-h  permits  their  maintenance. 

Results  of  Pyorrhea  Alveolaris. — Until  recently  little  attention  has 
been  given  by  either  the  medical  or  dental  profession  to  the  appalling 
results  often  attending  pyorrhea  alveolaris.  The  dental  profession 
has  recognized  the  destructive  effect  locally,  but  not  to  the  fullest 
extent.    Such  conditions  as  death  of  the  dental  pulp,  necrosis  of  the 


PROGNOSIS  2G5 

bone,  empyema  of  the  antrum,  and,  in  fact,  every  pathological  con- 
dition common  to  the  nioutli  often  has  as  its  starting-point,  pyorrhea 
alveolaris. 

What  is  even  more  common  and  serious,  is  the  great  variety  of  sys- 
temic effects  of  this  disease.  Pus,  septic  discharges,  toxins,  and  the 
organisms  themselves  enter  the  system,  both  by  ingestion  and  direct 
absorption,  are  carried  to  every  part  of  the  anatomy,  and  establish 
pathological  conditions  which  are  often  fatal. 

Such  eminent  medical  authorities  as  Drs.  Osier,  Hunter,  Mayo  and 
others,  regard  mouth  infections  as  the  frequent  source  of  such  sys- 
temic diseases  as  all  forms  of  digestive  disturbance  including  appen- 
dicitis, nephritis,  endocarditis,  colitis,  rheumatic  fever,  arthritis 
deformans,  septicemia,  anemia,  general  toxemia,  tonsilitis  and 
])haryngitis,  gastric  ulcer,  abscess  of  glands  and  other  tissues,  such  as 
carbuncles,  and  all  conditions  having,  as  their  origin,  infection. 

Even  the  common  communicable  diseases  are  fostered  by  infected 
mouths.  Statistics  show  a  remarkable  decrease  of  such  diseases  in 
institutions  where  oral  sanitation  is  practised. 

Prognosis. — When  correct  treatment  of  pyorrhea  alveolaris  has 
been  conducted,  and  proper  prophylactic  measures  carried  out  subse- 
quently, there  is  practically  no  such  thing  as  recurrence.  When  there 
is  a  continuance  or  recurrence,  it  is  almost  invariably  due  either  to 
lack  of  knowledge  or  skill  on  the  part  of  the  operator,  or  failure  on 
the  part  of  the  patient  to  carry  out  instructions;  presuming,  of  course, 
that  proper  instructions  have  been  given. 


CHAPTER  XI. 
ODONTALGIA  AND  ALVEOLAR  ABSCESS. 

By  M.  L.  RHEIN,  AI.D.,  D.D.S.,  D.R.C.,  U.S.N. 

ODONTALGIA. 

There  is  nothing  that  has  a  greater  horror  for  the  world  at  large 
than  toothache.  To  the  layman,  every  kind  of  pain  in  the  dental 
region  is  summarized  in  that  word.  The  variations  in  the  nature  and 
characteristics  of  such  pains  have  a  most  important  diagnostic  value. 

While  it  is  true  that  the  tales  of  woe  that  the  patient  sometimes 
relates  are  very  trying  to  the  listener,  nevertheless  it  behooves  the 
dental  hygienists  to  pay  the  most  careful  attention  to  the  details  of 
such  conditions,  if  they  expect  to  make  a  correct  report  on  conditions 
that  they  find. 

The  sensation  of  pain  is  transmitted  by  the  nervous  system.  The 
nerves,  as  they  ramify  tlirough  the  human  body,  can  readily  be  com- 
pared to  a  complicated  telegraph  line.  The  same  pair  of  nerves  that 
supply  the  dental  regions  go  to  the  eyes,  nose  and  ears.  An  irritation 
of  a  nerve  terminal,  frequently  is  not  felt  at  the  point  of  irritation, 
but  at  some  other  place,  which  may  be  the  most  remote  point  of  the 
body.  This  is  termed  referred  or  reflexed  pain.  Following  out  our 
telegraphic  simile,  the  shock  goes  direct  to  the  brain,  and  is  then 
transmitted  to  the  terminal  of  some  other  line.  Consequently,  it  is 
always  well  to  bear  in  mind  the  possibility  of  almost  all  forms  of  pains 
having  a  dental  origin. 

The  most  common  form  of  toothache  is  that  produced  by  the  inroads 
of  dental  caries.  As  the  enamel  is  at  the  very  first  destroyed,  there  is 
very  little  sensation,  because  the  inner  layer  of  dentin  endeavors  by 
nutritional  changes  to  protect  itself.  As  caries  approaches  nearer 
the  pulp,  there  comes  a  place  where  this  protection  ceases,  and  where 
the  slightest  thermal  change  causes  intense  pain.  Heat,  cold  or  acid 
formations  all  produce  the  same  character  of  pain,  and  the  source  of 
this  jjain  is  very  easily  learned  by  observation.  The  entrance  of  the 
exphjrer  in  a  cavity  generally  suffices  to  expose  the  cause,  and  the 
case  becomes  one  for  the  dentist. 

There  is,  however,  another  form  of  odontalgia  which  should  be  of 
more  interest  to  the  dental  hygienist.  Without  entering  into  the  the- 
ories of  erosion,  it  is  sufficient  to  say  that  under  certain  circumstances 
the  enamel  is  dissolved.  This  is  most  likely  to  take  place  at  the  gin- 
gival margin  on  either  buccal  or  lingual  surface,  and  frequently  is 
followed  by  the  most  exquisite  sensitiveness.     The  patient  will  gen- 


ODONTALGIA  267 

erally  call  attention  to  the  pain  ])ro(Iuced  when  these  surfaces  are 
polished,  in  contrast  to  the  feeling  of  intense  satisfaction  produced  by 
proper  manipulation  of  the  orange-wood  stick  over  an  ordinary  enamel 
surface.  Careful  observation  will  demonstrate  the  fact  that  the 
gingivae,  which  for  years  have  not  been  massaged  or  cleansed,  generally 
covers  these  most  sensitive  areas. 

Not  uncommonly  is  it  the  case  that  the  pain  caused  by  such  erosions 
has  made  the  patient  apply  to  the  dentist.  Often  the  distress  will 
be  so  great  that  the  patient  is  positive  that  the  ofi'ending  teeth  mi^t 
be  lost.  There  is  nothing  that  regular  proi)hylactic  care  will  serve 
better  than  the  cure  or  alleviation  of  such  distress.  Consequently, 
the  hygienist  is  able  to  give  such  cases  a  very  favorable  prognosis  if 
the  patient  will  carefully  follow  out  the  proper  daily  hygienic  care 
of  the  mouth. 

In  such  cases  the  terminal  circulation  has  become  impaired,  and 
the  result  is  an  abnormality  in  the  excretion  of  the  mucous  follicles. 
Debris  of  foodstuffs  fermenting,  leave  an  acid  condition,  and  together 
with  this,  are  found  bacterial  plaques. 

All  these  combined  factors  ])roduce  the  subsequent  enamel  dete- 
rioration. The  proper  use  of  the  orange-wood  sticks  under  the  gingival 
margin  of  the  gums  will,  in  conjunction  with  frequent  gum  massage 
by  the  patient,  tend  to  restore  these  tissues  to  a  normal  condition.  Of 
course  enamel  that  has  been  lost  cannot  be  restored,  but  when  the 
inroad  of  erosion  has  stopped,  the  solution  of  the  enamel  surface 
ceases,  and  after  a  while  the  dentin  acquires  a  surface  somewhat 
similar  to  enamel  and  the  sensitiveness  disappears. 

There  are  other  forms  of  pain  that  come  under  the  head  of  neural- 
gias or  tic  douloureux.  These  vary  greatly  in  their  symptomatology. 
There  may  be  a  sudden  sharp,  piercing  pain,  or  on  the  contrary,  a 
pulsating  throb.  This  pain  may  occur  at  regular  or  irregular  inter- 
vals. Pressure  on  nerve  fibers  is  generally  regarded  as  the  cause  of 
such  trouble.  In  exostosis  of  the  roots  of  teeth  we  find  a  common 
cause.  As  the  roots  thicken  in  size  they  begin  to  occup}'  a  space  that 
had  been  tenanted  by  something  else,  and  pressure  on  the  peri-apical 
tissues  is  created;  if  the  pressure  is  exerted  against  nerve  fiber,  one  of 
the  most  severe  forms  of  neuralgia  is  likely  to  ensue. 

An  abnormal  supply  of  nutrition  to  the  cementum  is  the  cause  of 
exostosis.  The  Roentgen  rays  make  the  diagnosis  very  easy,  where 
formerly  it  was  one  of  the  most  difficult  of  conditions  to  diagnose.  In 
like  manner  the  calcific  deposits  in  the  pulp  are  produced  by  extra- 
ordinary nutritional  disturbances.  These  deposits  vary  greatly  in  size, 
shape  and  appearance.  They  may  simulate  minute  seeds,  nodules 
or  pulp  stones  of  more  or  less  rounded  shape,  or  they  may  be  jagged 
and  star-shaped.  They  may  appear  to  coalesce  and  form  one  large 
mass  of  inorganic  material,  completely  occluding  the  pulp  chamber. 
It  does  not  take  much  imagination  to  conclude  that  a  star-shaped 
and  jagged  pulp  nodule  pressing  on  nerve  fibrils  will  produce  very 


268  ODONTALGIA   AND  ALVEOLAR  ABSCESS 

great  pain.  Fortunately  the  roentgenogram  here  affords  great  diag- 
nostic assistance. 

There  are  two  forms  of  toothache  that  have  a  very  important  bear- 
ing on  the  study  of  the  symptomatology  of  alveolar  abscess.  The 
following  is  a  typical  histbry:  The  tooth  is  aching  badly,  especially 
when  subjected  to  cold  and  heat.  It  becomes  very  sensitive  to  the 
touch.  One  morning,  on  awakening,  the  individual  is  very  happy  to 
find  that  all  pain  has  ceased.  Ice-water  no  longer  produces  this  inde- 
scribable pain.  The  pulp  in  the  tooth  has  lost  its  vitality.  The  sense 
of  security  on  the  part  of  the  individual  is  not  well  placed.  About 
a  week  later  a  sudden  intense  pain  is  experienced  from  heat  that  may 
reach  the  tooth.  Cold  now  has  a  tendency  to  bring  relief,  but  heat 
only  produces  a  typical  neuralgic  effect.  During  this  interval  pyogenic 
bacteria  have  gained  entrance  to  the  pulp  chamber,  and  infection  of 
this  organic  tissue  has  begun.  The  tooth  has  now  become  exceedingly 
sensitive  to  the  slightest  touch.  On  opening  the  pulp  chamber  the 
pulp  will  be  found  more  or  less  purulent,  and  the  indescribable  but 
well-known  odor  of  dead  pulp  adds  to  the  unpleasantness.  An  incip- 
ient alveolar  abscess  has  already  started  in  the  peri-apical  region. 
This  is  the  acute  stage  of  alveolar  abscess. 

The  pain  that  is  caused  from  a  dying  pulp  is  almost  the  antithesis 
of  the  pain  produced  by  an  incipient  alveolar  abscess.  It  is  frequently 
difficult  to  demonstrate  to  laymen  that  the  severest  form  of  tooth- 
ache can  be  present  after  the  pulp  is  dead.  It  is,  however,  of  supreme 
importance  that  this  differentiation  in  the  character  of  the  pain,  when 
the  pulp  is  dying  and  that  experienced  where  later  infection  of  the 
pulp  has  taken  place,  should  be  thoroughly  mastered  by  the  dental 
hygienist. 

The  primary  object  of  introducing  odontalgia  in  this  chapter  is 
for  the  very  purpose  of  impressing  on  the  dental  hygienist,  the  ne- 
cessity of  being  able  to  differentiate  between  the  various  forms  of 
odontalgia  of  which  the  patient  will  complain. 

It  is  important  that  the  initial  symptoms  of  a  dying  pulp,  as  indi- 
cated by  the  character  of  the  pain,  should  be  thoroughly  mastered, 
as  such  a  case  should  have  immediate  dental  service.  Dental  atten- 
tion may  })e  postponed  in  such  cases,  without  any  further  detriment 
than  the  suffering  of  the  patient.  When,  however,  the  pulp  has  once 
died,  and  the  tenderness  and  sensitiveness  to  heat  indicates  the  onset 
of  infection  in  the  pulp  chamber,  no  delay  of  operative  treatment  is 
excusable.  A  difference  of  twenty-four  hours  in  opening  the  pulp 
chamber  of  such  a  tooth  may  have  a  vital  bearing  on  the  ultimate 
preservation  of  the  tooth.  At  this  time  the  pulp  chamber  should 
be  entered  with  extreme  care,  so  that  no  infection  is  forced  through  a 
foramen.  If  the  peri-apical  region  has  not  become  infected,  every  care 
should  be  taken  that  this  evil  be  avoided.  The  besetting  sin  of  dental 
operations  is  undue  haste  where  great  care  is  required  to  avoid  inju- 
rious consequences.     Time  plays  such  an  important  role  in  dental 


ALVEOLAR  ABSCESS  269 

therapy  that  manj^  good  dentists  have  been  known  to  yield  to  the 
temptation  of  hasty  procedure. 

The  dental  hygienist  will  frequently  be  found  at  the  side  of  the 
dental  chair  acting  in  the  capacity  of  a  trained  assistant  to  the  dentist. 
Possessing  a  knowledge  of  the  care  requisite  in  the  handling  of  such 
cases,  her  presence  will  unconsciously  act  as  a  brake  on  the  desire  of 
the  dentist  to  go  ahead  at  full  speed  without  regard  to  consequences. 
Even  when  infection  has  once  reached  the  peri-apical  region,  it  is  of 
the  greatest  importance  that  no  treatment  be  employed  that  will 
tend  to  increase  the  area  infected.  In  this  respect  too  great  caution 
cannot  be  urged  in  the  use  of  any  of  the  great  number  of  proprietary 
preparations,  which  depend  on  setting  free  formaldehyde. 

The  writer  has  a  keen  recollection  of  a  case  to  which  he  was  called 
in  consultation  by  a  much-worried  physician.  The  patient's  tempera- 
ture had  risen  to  105.5°.  It  was  a  case  of  acute  alveolar  abscess  of  an 
upper  incisor.  A  large  dressing  of  one  of  these  proprietary  nostrums 
had  been  placed  in  the  root  canal,  which  had  a  wide-open  foramen. 
The  great  amount  of  formaldehyde  passing  through  the  foramen 
mechanically  carried  the  infection  up  to  the  floor  of  the  nose.  Prompt 
surgical  measures  at  this  point,  at  least  one-half  inch  above  the  end 
of  the  root,  caused  the  temperature  to  drop  to  normal  within  twenty- 
four  hours. 

ALVEOLAR  ABSCESS. 

Between  ISSO  and  1890  the  science  of  bacteriology  began  to  have 
a  marked  influence  both  on  the  teaching  and  treatment  of  diseases 
of  the  body.  Since  that  time  the  achievement  of  bacteriologists  has 
produced  an  ever-changing  transition  in  the  point  of  ^'iew  of  mouth 
conditions.  This  change  in  the  treatment  of  disease  has  been  much 
more  rapid  in  other  parts  of  the  body  than  in  the  mouth,  and  this  is 
due  to  the  fact  that  a  large  percentage  of  dentists  are  not  medically 
trained  men. 

It  is  worthy  of  note  in  this  respect  that  one  of  the  earliest  works 
of  value  was  the  production  of  a  dentist.  Dr.  W.  I).  Miller,  at  that  time 
of  the  University  of  Berlin,  who  published  in  1890  his  classical  work 
on  microorganisms  of  the  mouth.  The  stimulus  of  this  work  in  itself 
would  have  kept  the  scientific  progress  of  dentistry  on  a  par  with  that 
of  the  rest  of  medicine  if  the  majority  of  dentists  had  been  medically 
educated.  The  eyer-widening  gap  between  dentistry  and  medicine, 
since  ^Miller's  work  was  published,  has  been  due  to  this  unfortunate 
condition  of  affairs.  It  is  impossible  to  separate  one  part  of  the  body 
from  another.  ^Microorganisms  that  are  found  in  the  mouth  may 
reach  every  part  of  the  body.  When  disease  becomes  a  serious  matter 
it  is  found  that  the  infecting  microorganisms  use  the  lymph  channels 
and  other  media  of  circulation  and  by  their  own  motile  force  they 
travel  to  any  part  of  the  body.  Consequently,  it  is  only  a  question  of 
time  when  no  one  will  be  permitted  to  commence  the  practice  of 


270  ODOXTALGIA   AXD  ALVEOLAR  ABSCESS 

dentistry  unless  thorouglily  educated  in  the  study  of  health  and 
disease. 

It  is  on  account  of  this  absence  of  pathological  knowledge,  due  to  the 
lack  of  general  medical  education,  that  this  subject  is  so  inadequately 
understood  by  the  majority  of  dental  practitioners.  The  hygienist 
is  to  be  educated  to  work  in  a  field  where  the  possibilities  of  infection 
caused  by  some  of  these  microorganisms  should  be  constantly  borne 
in  mind.  It  is  important  that  the  danger  involved  should  be  appre- 
ciated. Even  if  ^-ith  the  utmost  care  the  hygienist  does  not  help  to 
produce  infections,  there  must  also  be  steadfastly  in  her  mind  the  possi- 
bility of  aggravating  infected  areas  if  the  dentinal  tissues  are  handled 
without  a  due  appreciation  of  this  danger. 

Abscesses  are  infectious  degenerations  of  tissue.  They  are  the 
result  of  an  infection  produced  by  some  form  of  pyogenic  bacteria. 
These  bacteria  yield  in  turn  various  kinds  of  toxins,  which  become 
the  real  agents  of  tissue  destruction.  AMien  the  organism  is  of  a  hemo- 
lytic or  blood-dissolving  type  of  sufficient  virility,  it  produces  irrita- 
tion, inflammation,  and  a  resultant  breaking  down  of  the  tissues  into 
pus.  Where,  however,  the  bacteria  have  a  very  low  power  of  virility, 
like  the  Streptococcus  viridans,  the  tissues  do  not  break  down  into 
pus,  but  nevertheless  toxins  are  produced. 

When  it  is  considered  that  at  all  times  the  mouth  is  filled  with  living 
bacteria,  the  ever-present  danger  of  the  individual  to  infection  cannot 
but  be  apparent  to  any  observer.  If  it  was  not  for  what  is  spoken 
of  as  the  immunity  of  the  individual,  human  life  on  this  planet  would 
have  long  since  ceased  to  exist;  but  there  are  certain  forms  of  cells 
that  act  as  a  protecting  army  against  these  attacking  forces.  This 
defensive  power  is  lodged,  to  a  large  degree,  in  the  white  blood  cor- 
puscles or  leukocytes.  The  gum  tissue  itself,  when  unwounded,  is  a 
defensive  agent.  There  are  also  certain  elements  in  the  blood  itself, 
which  help  to  maintain  this  condition  known  as  immunity.  While 
in  this  state  the  pathogenic  bacteria  have  practically  no  effect  against 
the  defense  which  the  individual  possesses.  There  comes  a  period  or 
periods  in  ever}'  human  life  when  this  defense  becomes  weakened, 
and  then  infection  is  likely  to  take  place  in  some  part  of  the  body. 
When  this  period  arrives,  the  area  to  become  infected  is  that  part 
of  the  body  which  offers  the  least  resistance.  This  state  is  known  as 
locus  minonis  resistentice.  In  other  words,  the  place  with  the  least 
resistance  is  thg  spot  that  the  bacteria  seek  out  when  this  defense 
becomes  more  or  less  weakened.  If  an  indi\'idual  has  in  his  mouth  one 
or  more  teeth  which  have  been  ineffectually  treated,  where  imperfect 
pulp  removal  and  imperfect  root-canal  filling  has  been  done,  this  place 
will  be  at  once  invaded  by  the  hostile  bacteria  as  the  point  of  least 
resistance,  and  is  therefore  likely  to  become  the  infected  area. 

Unfortunately,  an  inferior  type  of  constructive  dentistry  plays  a 
very  important  role  in  leaving  places  of  this  kind  in  the  dental  region. 

The  great  demand  in  this  country  for  dentistry  at  a  moderate  price 


ALVEOLAR  ABSCESS 


271 


has  been  one  of  the  greatest  causes  of  this  unfortunate  condition  of 
affairs.  A  tooth  in  which  pulp  work  has  been  done  imperfectly,  may- 
retain  a  comparatively  healthy  condition  as  long  as  the  individual 
retains  this  state  of  immunity.  This  condition  is  frequently  destroyed 
by  the  intervention  of  some  other  infectious  disease,  as  for  example, 
a  severe  attack  of  influenza,  which  is  very  epidemic  at  certain  times 
of  the  }'ear  in  this  country.  The  weakened  condition  of  the  individual, 
from  an  attack  of  this  nature,  at  once  impairs  his  immunity  and  the 
parts  about  this  imperfect  dental  constructive  work  become  the  place 
of  least  resistance  which  the  pyogenic  bacteria  attack.  In  the  same 
manner,  imperfect  mastication  and 
faulty  assimilation  of  food,  lack  of 
attention  to  common-sense  rules 
of  hygiene,  and  numerous  other 
factors  of  this  nature,  in  fact  age 
itself,  tend  to  depreciate  more  or  less 
at  times  this  condition  of  immunity 
and  thus  to  bring  the  individual  into 
a  state  where  infection  becomes 
possible. 

For  the  sake  of  convenience, 
these  abscesses  may  be  considered 
in  their  principal  forms,  acute  and 
chronic.  The  initial  attack  is  gen- 
erally spoken  of  as  an  acute  al- 
veolar abscess.  It  begins  with  a 
local  generation  of  heat,  rise  in 
body  temperature,  constantly  in- 
creasing inflammation,  and  edema 
of  the  localized  infected  area. 
Then  pus  forms,  and  if  the  ab- 
scess produced  is  not  opened  f,«.  ^S.-Acute  alveolar  abscess  of  a 
surgically,  it  seeks  release  from  lower  incisor  in  the  third  stage,  with  pus 
its    environment    bv    the    path     of      ca\-ity  between  the  bone  and  the  peri- 

Ipflst  rpsistnnpp  This  is  P-pnerallv  o^t^"™-  ^'  P^^  ^^^'^^^  ^^  t^^  bone;  b, 
least    resistance.       iniS   is  generain       p^g  between   the   periosteum  and  bone; 

through    the     plate    of     the     alveo-      c,  lip;    d,  tooth;    e,  tongue.     (Black.) 

lus;  sometimes,  however,  it  follows 

the  sheaths  of  the  tissues  and  is  evacuated  at  some  remote  point, 
which  always  makes  the  diagnosis  of  the  locus  of  infection  of  such 
cases  more  difficult.  Abscesses  of  this  nature  have  often  been  known 
to  discharge  into  the  clavicular  region,  and  much  more  frequently 
through  the  cheeks  of  individuals.  (Fig.  115.)  When  the  active 
symptoms  of  an  attack  of  this  kind  have  subsided,  as  they  will 
after  a  time  even  without  treatment,  the  abscess  assumes  a  latent 
form  and  now  is  spoken  of  as  a  chronic  alveolar  abscess.  It  is  not 
an  uncommon  thing  for  dentists  to  assure  their  patients  that  an 
abscess  has  been  ciu-ed  because  its  active  symptoms  have  disappeared, 


979 


ODONTALGIA  AND  ALVEOLAR  ABSCESS 


when  perhaps  in  a  month  or  six  months,  or  in  a  year  or  years, 
it  may  break  out  afresh,  and  thus  show  that  it  has  not  been 
cured.  These  outbursts  of  a  chronic  abscess  are  generally  attended 
with  none  of  the  pain  and  discomfort  which  accompany  the  initial 
attack.  They  are  often  spoken  of  as  harmless  little  gum  boils,  instead 
of  being  recognized  as  a  very  powerful  factor  in  breaking  down  immu- 
nity. The  extent  of  inflammation  which  takes  place  as  a  result  of  infec- 
tion of  this  kind,  is  dependent  upon  the  nature  of  the  infecting  organ- 
isms. These  vary  largely  in  their  degree  of  virility.  The  more  powerful 
microorganisms  are  of  a  hemolytic  type,  and  produce  the  ordinary 
acute  alveolar  abscess.  A  much  more  dangerous  organism,  however, 
is  non-hemolytic,  generally  one  of  the  streptococci,  which  possesses  so 
small  an  amount  of  virulence  that  it  is  frequently  incapable  of  produc- 
ing a  degree  of  inflammation  sufficient  to  cause  an  irritation  that  will 
be  appreciable  to  the  affected  individual.  As  a 
result  of  this  low  degree  of  inflammation,  nature 
builds  up  a  defensive  line  of  fibrous  tissue  around 
the  infected  area,  which  in  a  short  time  becomes 
a  regular  envelope  entirel}^  covering  the  abscess 
tract.  The  product  is  known  as  a  granuloma 
or  blind  abscess,  perhaps  the  most  serious  in- 
fective result  that  could  be  produced  (Fig. 
116). 

In  the  dental  region,  a  granuloma  may  become 
encased  in  the  alveolar  structure  in  the  peri- 
apical space,  where  it  may  be  unnoticed  and 
dormant  for  years.  However,  it  forces  through 
this  fibrous  envelope  into  surrounding  tis- 
sues, injurious  toxins  or  products  of  its  mul- 
tiplication. These  toxins  are  carried  by  the  lymph  channels  to  the 
various  organs,  where  their  energy  gradually  tends  to  undermine 
these  organs  and  to  produce  grave  chronic  diseases,  among  which 
may  be  mentioned  arthritis  deformans.  It  is  now  well  recognized 
that  many  instances  of  grave  cardiac  disease  of  an  infectious  type 
can  be  traced  back  to  untreated  alveolar  abscesses. 

Dental  Pulp. — In  considering  this  topic,  a  thorough  understanding  of 
dental  histology  is  necessary.  It  is  especially  important  to  remember 
the  division  of  this  tissue  into  inorganic  and  organic.  Inorganic 
material  itself  is  not  capable  of  becoming  infected,  but  there  is 
always  strata  of  organic  matter  intermixed  with  the  inorganic,  which, 
becoming  infected,  help  to  break  down  the  inorganic  tissue.  The 
pulp  of  the  tooth  in  a  normal  condition  is  entirely  of  organic  nature, 
and  thus  open  to  infection,  as  it  affords  an  inexhaustible  supply  of 
nutriment  for  pyogenic  bacteria.  Perha])s  the  most  imj)ortant  single 
feature  of  the  pulp  is  its  vascularity.  As  long  as  it  retains  a  normal 
blood  circulation,  infection  of  tins  jelly-like  mass  is  impossible. 
There  are  various  wavs  in  which  the  normal  circulation  becomes 


Fig.  116. — Granulomata 
or  blind  abscesses. 


ALVEOLAR  ABSCESS 


273 


impaired,  and  the  pulp  loses  its  vitality.  Dental  caries  is  perhaps  the 
most  common  cause.  The  inflammation  resulting  from  this  disease 
invariably  reacts  on  the  pulp,  manifesting  itself  in  various  wa>'s. 
It  may  lead  to  fatty  degeneration,  or  abnormal  fungous  hypertrophy, 
etc.  Under  the  conditions  of  caries  near  the  pulp,  it  readily  becomes 
the  prey  of  invading  bacteria  with  resulting  infection  (Fig.  117). 


i 


■■», 


Fig.  117. — Fatty  degeneration  of  the  pulp. 


The  irritation  of  the  pulp,  whether  from  caries  or  other  causes,  often 
produces  an  entirely  different  abnormal  condition.  Under  certain 
conditions,  there  appears  to  be  an  effort  of  nature  to  protect  the  organ, 
and  this  results  in  an  excessive  supply  of  inorganic  material  which 
in  turn  results  in  a  calcific  degeneration  of  the  pulp.  This  condition 
is  usually  found  in  adult  life,  becoming  more  marked  as  age  advances. 
It  is  found  in  very  varied  circumstances.  The  pulp  may  be  found  im- 
pregnated with  little  seed-like  bodies,  crystalline  in  their  formation. 
From  just  a  few  of  these  pulp  nodules,  the  degeneration  may  progress 
18 


274 


ODONTALGIA   AND  ALVEOLAR.  ABSCESS 


until  the  entire  pulp  is  found  to  be  practically  calcified  with  just  a 
microscopic  strata  of  organic  structure  permeating  it  (Fig.  118). 

This  calcification  often  has  a  tendency  to  strangulate  the  already 
impaired  circulation,  and  thus  produce  death  of  the  pulp.  The 
proper  removal  of  such  a  pulp  is  no  mean  surgical  triumph,  and 
will  l)e  referred  to  later. 

Injudicious  dental  operations  in  the  shape  of  large  metallic  fillings 
in  close  proximity  to  the  pulp,  are  frequent  sources  of  the  irritation 
producing  this  degeneration  and  subsequent  death  of  the  pulp.  Acci- 
dents are  frequent  causes  of  traumas  resulting  in  a  rupture  of  the 
bloodvessels  entering  the  foramina  and  thereby  causing  the  death  of 
the  pulp. 


Fig.  118. — Pulp  calcification. 


The  pulp  having  died,  the  tooth  is  left  with  this  dead  body  in  its 
interior,  a  prey  to  the  first  invading  bacteria.  Consequently,  it  is  essen- 
tial that  the  corj)se  be  speedily  removed.  This  means  the  removal 
of  every  particle  of  organic  tissue  under  strictly  aseptic  precautions, 
and  the  hermetic  sealing  of  the  root  canal.  There  is  a  type  of  these 
cases  in  which  th(;  pulp  does  not  die,  but  as  the  calcification  progresses 
to  almost  the  })oint  of  ()l)literation,  a  severe  inflammation  of  the  end 
of  the  root  and  peridental  tissues  takes  ])lace.  This  inflammatory 
process  is  caused  by  the  microscopic  elements  of  organic  tissue  left  in 
the  pulp.  The  pericementitis  is  often  very  severe,  and  is  accompanied 
by  serous  exudation  around  the  necks  of  the  teeth.  Only  the  cleans- 
ing of  such  canals  through  every  foramina  will  cure  this  condition. 
An  inflammatory  exudate  from  this  source  is  only  too  frequently  diag- 


ALVEOLAR  ABSCESS 


275 


nosed  as  })yorrliea  alveoliiris,  especially  when  the  tooth  sliows  signs 
of  loosening.  All  the  recognized  treatments  for  pyorrhea  only  increase 
the  inflammatory  conditions,  hut  when  the  organic  matter  has  been 
conii)letely  removed  so  that  a  broach  will  i)ass  through  every  foramen, 
the  tooth  will  at  once  tighten  in  its  socket  and  all  exudate  will  cease. 

The  symptoms  following  infection  depend  largely  on  the  nature  of 
the  infecting  organism.  When  it  is  of  the  hemolytic  variety,  pus  soon 
develops,  and  the  extent  of  tissue  invaded  varies  greatly.  Cases  of 
this  type  are  frequently  diagnosed  and  treated  as  pyorrhea  alveolaris. 
To  many  medical  men,  as  well  as  to  many  dentists,  this  is  the  only 
answer  to  the  problem  of  pus  in  the  mouth.  Radiography  has  made 
the  correct  diagnosis  of  such  conditions  a  comparatively  easy  matter. 

It  is  inexcusable,  at  the  present  time,  to  treat  a  supposedly  pyorrheal 
mouth  without  first  studying  the  roentgenograms  of  such  a  mouth. 
An  alveolar  abscess  with  a  fistulous  opening  at  the  gingival  border, 
while  very  deceptive  from  the  standpoint  of 
physical  examination,  becomes  easy  of  diag- 
nosis in  studying  a  properly  focussed  roent- 
genogram. The  destruction  of  alveolar  struc- 
ture around  the  end  of  the  root  makes  this 
diagnosis  very  simple.  While  a  pseudo  form 
of  pyorrhea  may  develop  from  the  pus  dis- 
charging around  the  neck  of  a  tooth,  all 
methods  of  treating  the  pyorrheal  condition 
must  fail,  unless  the  pulp  of  the  tooth  is 
properly  removed  and  the  diseased  structure 
in  the  peri-apical  region  is  completely  erad- 
icated (Fig.  119). 

In  almost  all  cases  of  pulps  dying  from 
trauma,  and  frequently  where  the  infecting 
microorganism  attacks  the  foraminal  entrance 
in  the  peri-apical  region,  the  bacteria  are  of  a 

non-hemolytic  variety,  and  most  generally  when  isolated  are  found  to 
be  the  Streptococcvs  viridans.  It  is  a  well-noted  clinical  fact  that  this 
attenuated  form  of  streptococcus  is  not  uncommon  in  this  region. 

Wherever  partial  pulp  removal  is  practised,  and  any  method  of  med- 
ication of  the  remnant  of  the  pulp  tissue  is  employed,  with  the  object 
of  making  the  parts  immune  to  infection  (a  procedure  known  gener- 
ally as  a  mummifying  process),  the  pulp  tissue  is  invariably  subject  to 
infection  at  its  peri-apical  entrance  into  the  root  canal.  The  virility 
of  the  viridans  organism  is  so  slight  that  no  active  inflammatory 
action  takes  place,  and  pus  is  not  formed.  As  the  Streptococcus  viridans 
makes  a  habitat  in  the  foramen  at  the  end  of  the  root,  a  protecting  ring 
of  fibrous  tissue  is  formed  around  this  point.  It  is  a  mooted  question 
whether  this  envelope  of  the  granuloma  is  intended  as  a  protection 
to  invasion  of  the  tissues,  or  whether  it  is  a  protection  to  the  strep- 
tococci against  leukocytes  or  other  antagonistic  elements. 


Fig.  119.  —  Roentgen- 
ogram showing  alveolar 
abscess  erroneously  diag- 
nosed as  pyorrhea  alveo- 
laris. 


276  ODONTALGIA   AND  ALVEOLAR  ABSCESS 

The  fact  remains,  hoAvever,  that  from  these  infective  foci,  toxins 
may  be  constantly  sent  into  the  rest  of  the  body.  It  is  a  very  generally 
recognized  fact  that  the  toxins  from  different  microorganisms  appear 
to  have  a  selective  affinity  for  certain  tissues.  The  toxins  emanating 
from  these  granulomas  appear  to  have  such  a  selective  affinity  for 
the  muscles  and  valves  of  the  heart.  The  most  unfortunate  feature  in 
connection  with  this  type  of  alveolar  abscess  is  the  insidious  manner 
in  which  it  strikes  at  the  individual's  vital  forces.  Its  lack  of  virulence 
appears  to  make  it  incapable  of  producing  severe  local  irritation,  and 
consequently  a  dangerous  toxemia  may  be  progressing  without  the 
slightest  local  manifestation. 

With  the  present-day  knowledge  of  mouth  sepsis,  the  physician  is 
much  more  frequently  referring  cases  of  general  infection  to  the  dentist 
for  his  opinion  as  to  whether  a  septic  focus  is  present  in  any  part  of 
the  dental  region. 

Heretofore  the  dentist  has  simply  demonstrated  his  incompetency  in 
returning  a  verdict  of  an  aseptic  mouth  based  simply  on  ordinary  mouth 
examination.  Only  a  careful  roentgenogram  examination  of  each  indi- 
vidual tooth  socket  will  show  the  presence  of  these  blind  abscesses. 
The  importance  of  the  dental  opinion,  when  a  patient  has  been  referred 
by  the  physician  for  a  careful  examination,  has  never  in  the  past  been 
properly  appreciated.  In  the  future,  for  a  dentist  to  say  that  a  mouth  is 
free  from  infection,  however  beautiful  and  physiological  it  may  appear, 
he  must  first  carefully  study  the  roentgenograms  of  every  tooth  in  the 
mouth.  Unless  the  dentist  has  such  roentgenograms  of  the  entire 
jaw  and  mandible  at  his  disposal  for  study,  he  is  incapable  of  giving  an 
answer  to  this  all-important  question.  The  various  types  of  arthritis, 
ulcers  of  the  stomach,  gall-stones  and  kindred  toxic  diseases,  have 
had  their  origin  definitely  traced  to  abscesses  about  the  teeth. 

PERICEMENTAL  ABSCESS. 

There  is  still  another  form  of  abscess  which  closely  simulates  the 
alveolar  abscess,  and  may  exist  for  years  without  interfering  with  the 
vitality  of  the  pulp  of  the  tooth  in  the  region  of  the  abscess.  It  has  no 
etiological  connection  with  the  dental  pulp.  It  is  called  pericemental 
abscess,  because  the  localized  infection  is  found  in  the  pericementum 
around  the  roots  of  the  teeth.  The  most  acceptable  theory  of  the 
formation  of  these  abscesses  is  that  in  the  pericementum  is  left  some 
remnant  of  the  epithelium  from  which  the  original  enamel  germ  was 
formed.  These  remnants  of  epithelium  become  infected  in  the 
same  manner  as  does  the  organic  tissue  left  at  the  peri-apical 
end  of  a  root-canal  foramen,  which  produces  a  blind  abscess.  Of 
course  no  one  can  say  that  this  theory  of  the  etiology  of  pericemental 
abscess  will  be  borne  out  in  the  final  studies  of  the  cause  of  this  malady. 
It  is,  however,  of  the  utmost  importance  that  in  the  diagnosis  of 
other  types  of  abscess  this  form  of  infection  be  pro])erly  excluded. 
In  the  past  pericemental  abscess  has  rarely  been  correctly  diag- 


PERICEMENTAL  ABSCESS  277 

nosed.  Like  the  ordinary  alveolar  abscess,  it  is  most  frequently  called 
pyorrhea  alveolaris.  Many  men  of  ability,  who  have  been  able  to 
exclude  the  symptoms  of  a  pyorrhea,  have  erred  in  supposing  it  to  be 
an  ordinary  alveolar  abscess.  Here,  also,  the  roentgenogram  has  proved 
of  the  greatest  value  in  making  possible  correct  diagnosis  (Fig.  120). 

Treatment. — In  the  treatment  of  pericemental  abscesses,  ionism  has 
been  found  the  most  useful  agent  for  their  cure.  Frequently,  however, 
even  though  the  pulp  does  not  appear  to  be  involved,  it  becomes 
necessary  to  remove  this  organ  before  a  cure  can  be  effected. 

It  may  not  be  out  of  the  way  at  this  time  to  deprecate  the  growing 
tendency  to  the  use  of  the  term,  pyorrhea  specialists.  It  should  be 
clearly  understood  that  pyorrhea  alveolaris  is  only  a  symptom  of 
something  wrong  in  the  equilibrium  of  the  body. 

This  something  is  not  always  the  same  thing,  and  consequently 
the  cure  and  treatment  of  different  cases  of  pyorrhea  may  call  into 
therapeutic  requisition  any  one  of  all  the  known  dental  operations 
from  orthodontia  to  the  introduction  of  an  artificial  denture. 

Nearly  all  of  these  self-styled  special- 
ists begin  and  end  their  treatment  with 
the  pyorrheal  pocket  and  its  environ- 
ment. Such  men  succeed  in  doing  an 
incalculable  amount  of  harm.  While 
recognizing  the  great  benefits  to  be  de- 
rived from  the  various  specialties  in  den- 
tistry in  their  particular  field,  the  treat- 
ment of  pyorrhea  alveolaris  should  never 
be  termed  a  specialty,  because  its  sue-  fig.  120.  —  Roentgenogram  of 
cessful  therapy  may  demand  the  services  pericemental  abscess. 

of  not  only  any  one  of  our  recognized 

dental  specialists,  but  may  also  require  various  kindsof  medicaltreatment. 
In  this  respect  it  is  of  great  importance  to  be  able  to  differentiate 
between  physiological  and  abnormal  gum  tissue,  not  merely  in  a  gross 
manner,  but  with  all  the  niceties  of  gradations  in  color,  texture  and 
atrophy  or  hypertrophy  of  tissue.  To  be  able  to  differentiate  healthy 
from  abnormal  gum  tissue,  one  must  possess  minute  knowledge  of 
the  appearance  of  these  tissues,  which  is  only  gained  from  the  experience 
of  repeated  observations  with  this  point  in  view.  The  eyes  of  pro- 
phylactic operators  are  so  constantly  turned  on  these  tissues  that 
they  have  exceptional  opportunities  for  perfecting  themselves  in  these 
differential  observations.  The  gum  tissue  is  nourished  by  terminal 
capillaries,  which  leave  this  tissue  as  venous  blood.  The  extreme 
vulnerability  of  the  gums  is  due  to  the  fact  that  any  impairment  in 
nutrition  leaves  its  first  imprint  on  this  tissue. 

It  has  become  a  well-known  clinical  fact  that  the  effect  of  mal- 
nutrition upon  the  gums  varies  according  to  the  nature  of  the  cause. 
The  simplest  proof  of  this  fact  is  found  in  the  blue  staining  of  the  gums 
from  toxic  doses  of  mercury.  Physicians  for  many  years,  in  adminis- 
tering mercury,  have  been  accustomed  to  look  for  this  blue  stain  as 


278  ODONTALGIA  AND  ALVEOLAR  ABSCESS 

an  indication  that  medication  by  mercury  has  been  carried  to 
its  limit  of  safety.  In  Hke  manner,  every  grave  nutritional  disorder 
in  its  action  of  gum  starvation,  leaves  the  tissue  with  a  different  appear- 
ance, depending  upon  the  nature  of  the  organic  trouble. 

The  severity  of  the  disease,  and  consequent  extent  of  injury  to  the 
system,  to  a  certain  extent,  can  be  measured  by  the  amount  of  variation 
from  the  normal  appearance  of  gum  in  each  specific  case.  Some  of 
these  ^  variations  may  be  very  slight  and  difficult  to  differentiate, 
while  others  may  be  widely  dissimilar.  For  example,  in  Bright's  disease 
the  gum,  while  slightly  inflamed,  is  paler  than  normal  tissue  at  the  gin- 
gival portion.  Its  real  specific  characteristic,  however,  consists  in  a 
narrow  whip-cord-like  hypertrophy  on  the  lingual  surfaces  about  one- 
sixty-fourth  inch  from  the  gingival  margin,  and  conforming  in  contour 
to  the  scalloped  shape  of  the  gingivae.  In  diabetes,  however,  the  char- 
acteristic appearance  is  quite  the  opposite.  The  inflammatory,  condi- 
tion is  much  more  marked,  giving  the  gums  an  angry,  dark  reddish  hue 
around  the  gingivse,  which  latter  are  very  spongy  in  consistency,  and 
have  lost  their  attachment  to  the  cementum.  The  gums  bleed  freely 
when  even  slightly  irritated.  When  the  mouth  has  been  left  open  for  a 
ver}^  short  period,  the  palatal  surface  loses  its  moisture,  and  assumes 
a  shiny  surface  similar  to  the  outer  skin  of  an  onion.  One  of  the  most 
characteristic  diagnostic  signs  in  the  dental  region  is  shown  in  those 
cases  where,  on  account  of  valvular  disease  or  other  heart  disorder, 
there  is  an  insufficient  power  in  the  force  of  the  arterial  circulation  as 
it  leaves  the  heart.  In  such  cases  the  gum,  extending  from  one-third 
to  one-half  inch  from  the  gingivse,  will  be  found  to  be  more  or  less 
cyanosed.  Above  the  dark  blue  area,  the  gum  has  the  normal  pink 
color.  There  is  no  blending  of  the  normal  pink  color  into  the  dark 
blue,  but  an  abrupt  transition  that  makes  the  diagnosis  of  circula- 
tory trouble  of  some  kind  a  very  simple  matter. 

The  writer  has  made  a  diagnosis  of  many  cases  of  tuberculosis  of 
the  lung,  simply  from  observing  the  abnormally  increased  excretion 
from  the  mucous  follicles.  This  wonderful  diagnostic  field  will  be 
found  especially  interesting  to  the  intelligent,  studious  and  observing 
hygienist.  It  should  not  be  thought  that  this  can  be  easily  mastered. 
It  will  take  much  observation  and  study  to  learn  to  subdivide  properly 
and  understand  the  different  appearances  in  different  cases.  By 
taking  a  sympathetic  attitude,  and  by  the  use  of  tact  and  judgment, 
it  is  easy  to  learn  the  physical  history  of  these  cases,  and  thus  study 
the  peculiar  characteristics  of  the  gums  in  different  forms  of  mal- 
nutrition. To  the  individual  who  has  the  talent  to  master  this 
differential  observation,  there  is  opened  a  wonderful  field  of  useful- 
ness. It  lies  in  the  province  of  the  dentist,  if  he  has  sufficient  ability, 
to  detect  incipient  signs  of  malnutrition.  It  is  written  in  indelible 
type  on  the  gums  long  before  urinalysis  discloses  any  tangible  sign. 

It  will  be  one  of  the  great  privileges  of  the  dental  hygienist  to  call 
the  attention  to  these  indexes  of  malnutrition. 


PERICEMENTAL  ABSCESS  279 

It  seems  scarcely  necessary  to  say  that  the  early  diagnosis  of  many 
such  conditions  frequently  means  a  possible  cure  at  that  period. 
Even  where  that  is  impossible,  it  often  means  a  considerable  prolonga- 
tion of  life  if  proper  treatment  is  pursued. 

Treatment  of  Alveolar  Abscess. — Alveolar  abscesses  may  be  divided 
into  two  classes,  acute  and  chronic.  In  the  latter  class  would  come 
the  division  of  granulomas  or  blind  abscesses.  An  acute  condition  of 
an  abscess  refers  to  the  initial  stage  of  infection,  where  for  the  first 
time  pus  is  about  to  form  in  the  peri-apical  region.  If  such  a  case 
is  seen  early  enough,  the  pulp  chamber  may  be  delicately  opened,  and 
a  dressing  of  tricresol  and  formalin  (formacresol,  Buckley)  placed  in 
the  pulp  chamber  and  sealed  in  place  with  oxyphosphate  of  zinc 
cement.  In  a  certain  number  of  cases,  seen  at  a  very  early  stage, 
an  abscess  can  be  aborted  in  this  manner.  In  most  cases,  however, 
when  such  an  infection  has  begun,  nothing  will  prevent  its  going  to 
the  point  of  resolution  with  the  resultant  flow  of  pus.  If  left  to  itself, 
the  pus  will  follow  the  line  of  least  resistance  and  will  finally  discharge 
explosively  into  the  mouth.  When  it  is  evident  that  this  result  is 
imminent,  heat  is  often  applied  to  hasten  the  advent  of  suppuration. 
It  is  during  this  stage  of  edema  and  inflammation  that  the  pain 
reaches  its  height,  and  consequently  every  effort  should  be  made  to 
bring  about  a  flow  of  pus,  and  thus  relieve  the  tension  of  the  other 
tissues.  At  the  very  earliest  moment  possible  the  infected  area  is  laid 
wide  open,  and  if  this  does  not  result  in  a  ready  flow  of  pus,  the  alveolar 
plate  is  pierced  and  an  outlet  established  for  any  pus  which  may  be 
present.  The  fistulous  canal  is  now  kept  open  with  gauze  packing, 
and  after  a  short  time  all  symptoms  of  pain  disappear.  It  is  now 
feasible  to  remove  the  infected  dead  pulp,  eradicate  the  pathological 
condition  in  the  peri-apical  region,  and  leave  the  tooth  in  a  sound  con- 
dition and  free  from  the  danger  of  reinfection.  In  this  respect  the  treat- 
ment is  practically  similar  to  the  cure  of  a  blind  abscess  or  granuloma. 

While  dental  hygienists  will  take  no  personal  part  in  the  operative 
procedure  of  pulp  removal,  they  should  have  a  thorough  theoretic 
knowledge  of  what  is  required,  not  only  for  the  removal  of  patho- 
logical conditions,  but  also  for  so  leaving  the  tissues  that  reinfection 
is  rendered  practically  impossible.  It  must  be  understood  that  there 
is  a  scientific  reason  for  every  procedure,  and  that  nothing  should  be 
done  which  is  empiric.  Too  many  men  of  recognized  ability  have 
been  satisfied  with  a  technic  which  results  in  leaving  the  field  free  from 
infection  when  this  operation  has  been  completed.  Nothing  short  of 
making  infection  in  this  locality  impossible  will  give  dental  surgery 
that  high  position  to  which  it  is  justly  entitled  in  the  field  of  pre- 
ventive medicine.  It  matters  little  what  method  is  pursued  if  this 
result  can  be  secured. 

To  accomplish  this  object,  it  is  necessary  that: 

1.  Every  particle  of  organic  tissue,  living  oT  dead,  must  be  removed 
from  the  canals. 


280  ODONTALGIA  AND  ALVEOLAR  ABSCESS 

2.  Any  diseased  tissue  in  the  peri-apical  region  must  be  entirely 
obliterated. 

3.  Infection  of  organic  structure  in  the  dentinal  tubuli  must  be 
guarded  against. 

4.  All  foramina  must  be  hermetically  sealed  both  within  the  canal 
and  on  its  peri-apical  area. 

5.  Infection  from  the  region  of  the  pulpal  chamber  must  be  made 
impossible. 

The  time  has  come  when  it  must  be  recognized  that  all  five  of  these 
requirements  must  be  met.  No  compromise  can  be  permitted  in 
order  to  safeguard  the  future  health  of  the  individual.  If  for  any 
reason  any  one  of  these  results  cannot  be  attained,  the  tooth  must 
be  extracted. 

Where  diseased  conditions  have  not  advanced  too  far,  there  are  not 
more  than  three  or  five  per  cent,  of  teeth  that  cannot  be  scientifically 
operated  upon,  so  that  all  these  requirements  can  be  fulfilled.  This 
result,  however,  is  as  a  rule  only  possible  at  the  cost  of  many  hours  of 
work,  requiring  great  patience  and  skill  of  a  high  order.  This  always 
has  been  and  always  will  be  the  great  bar  against  the  practicability 
of  preserving  in  a  state  of  health  the  vast  majority  of  teeth  with  pulp 
involvement. 

Thousands  of  dentists  appear  to  think  that  if  the  interior  of  the 
root  canal  is  found  free  from  infection,  no  harm  can  result  from  such 
a  tooth.  They  appear  incapable  of  appreciating  the  fact  that  the 
little  blind  abscess  at  the  end  of  a  root  with  the  mildest  kind  of  a  strep- 
tococcus infection  is  the  most  dangerous  factor  that  can  be  left  in 
the  human  mouth.  It  can  now  be  seen  that  the  non-hemolytic  strep- 
tococcus of  low  power  of  virility  (so  low  that  it  is  incapable  of  pro- 
ducing sufficient  inflammation  to  produce  the  slightest  perceptible 
irritation)  is  continuously  sending  a  small  quantity  of  toxins  through 
the  system. 

It  is  fortunate  that  a  stage  where  these  facts  have  been  substantiated 
by  exact  laboratory  study  has  been  reached.  No  longer  can  the 
pompous  practitioner  assert,  "my  opinion  is  as  good  as  yours."  He 
must  be  made  to  realize  that  this  subject  has  passed  the  stage  of 
theory  to  one  of  established  scientific  proof. 

While,  therefore,  the  future  practice  of  dentistry  is  destined  to  bring 
the  practitioner  back  to  the  point  of  extracting  a  great  many  more 
teeth,  the  greater  value  of  the  natural  teeth  over  anything  artificial 
must  not  be  overlooked.  Efi'orts  at  conservation  of  hiunan  teeth  should 
not  be  lessened  wherever  such  a  consummation  is  feasible. 

Although  the  operative  technic  of  root  filling  does  not  come  within 
the  sphere  of  the  dental  hygienist,  the  writer  feels  warranted  in 
giving  in  detail  the  technic  of  the  improvement  to  which  he  has 
been  giving  continuous  attention  for  over  thirty  years,  so  that  this 
most  important  operation  in  dentistry  may  be  clearly  understood.  It 
is  his  fondest  hope  that  in  the  future  someone  will  unearth  a  method 


PERICEMENTAL  ABSCESS  281 

that  will  be  less  laborious  and  require  less  time,  but  up  to  the  present 
this  procedure  appears  to  meet  the  demand  more  thoroughly  than  any 
other. 

Only  since  the  introduction  of  the  .r-rays  has  it  been  possible  to  place 
root-canal  therapy  on  a  scientific  basis.  It  is  the  most  important  aid 
at  the  command  of  the  dentist  today  in  performing  a  scientific  opera- 
tion. It  is  continuously  required  from  the  outset  to  the  conclusion  of 
the  work.  It  is  important  before  beginning,  to  have  a  roentgenogram 
that  will  give  a  general  outUne  of  the  anatomy  of  the  roots  and  indi- 
cate if  any  pathological  condition  exists,  and  the  visible  extent  to 
which  tissue  destruction  has  taken  place. 

The  first  essential  in  the  mind  of  the  operator,  should  be  that  when 
the  operation  is  completed,  the  filling  material  must  seal  the  peri- 
apical end  of  the  root,  and  consequently  he  must  be  able  to  pass  a 
broach  through  every  foramen.  To  accomplish  this  it  is  essential 
that  the  point  of  entrance  to  each  root  canal  should,  as  nearly  as 
possible,  be  on  a  straight  line  with  the  foramen  at  the  end  of  the  root. 
By  the  aid  of  the  .x-rays  this  is  reduced  to  a  geometric  problem,  and 
many  teeth  can  have  apparently  badly  curved  roots  straightened  by 
making  the  point  of  entrance  at  the  correct  spot.  In  attaining  this 
object,  no  consideration  must  be  given  to  conservation  of  tooth  sub- 
stance. Having  solved  the  geometric  problem,  it  is  best  to  remove 
at  the  start  as  much  of  the  crown  as  it  will  be  necessary  to  remove 
at  any  stage. 

After  some  experience  this  can  be  readily  gauged.  Much  time  can  be 
sayed,  the  work  can  be  made  less  difficult,  and  better  results  can  be  ob- 
tained if  the  operation  of  removing  every  portion  of  tooth  to  be  removed 
is  completed  before  any  canal  is  entered.  There  are  cases  in  which  it 
may  be  necessary  to  remove  the  entire  crown,  and  where  a  root  is  to 
be  crowned,  it  is  naturally  far  preferable  to  do  this  at  the  outset.  The 
operator  must  become  thoroughly  familiar  with  the  ordinary  anatomy 
of  the  different  teeth  so  as  to  expedite  matters  as  much  as  possible. 
Where  living  pulp  is  to  be  removed,  it  is  supposed  to  be  previously 
anesthetized.  Before  the  pulp  chamber  itself  is  entered,  the  rubber 
dam  should  be  adjusted  and  the  field  of  operation  carefully  washed 
with  alcohol  or  a  ten  per  cent,  solution  of  formalin.  Every  possible 
precaution  should  be  taken  to  insure  strict  asepsis  at  every  stage  of 
the  operation.  If  a  live  pulp  is  to  be  removed,  a  perfect  Donaldson 
bristle  is  selected,  after  the  barbs  have  been  carefully  scrutinized 
under  a  magnifying  glass  to  insure  against  the  fracture  of  a  defective 
broach.  The  fine  Donaldson  barbed  broach  is  then  passed  gently 
alongside  of  the  pulp  tissue  as  near  the  end  of  the  canal  as  possible. 
Only  practice  can  bring  the  skill  that  the  delicate  manipulation  of 
this  broach  requires.  It  might  be  said  that  firmness  and  exquisite 
delicacy  of  manipulation  is  a  combination  of  application  that  is  neces- 
sary in  the  use  of  the  broach. 

It  is  requisite,  in  the  manipulation  of  the  broach  or  in  any  other 


2S2  ODONTALGIA   AND  ALVEOLAR  ABSCESS 

form  of  canal  instrumentation,  that  the  operator's  attention  should 
never  be  deflected  in  the  sliglitest,  because  of  the  danger  of  breaking 
an  instrument  in  a  root  canal. 

The  same  care  in  instrumentation  is  necessary  if  the  pulp  be  dead, 
lender  such  circumstances,  too  much  attention  cannot  be  devoted  to 
avoiding  the  forcing  of  any  infected  material,  however  minute,  through 
the  foramen.  It  is  frequently  an  error  of  judgment  to  prolong  instru- 
mentation too  far.  After  the  removal  of  all  masses  of  tangible  tissue, 
whether  living  or  dead,  or  in  any  particular  degree  of  decomposition, 
chemical  measures  must  be  employed. 

For  this  purpose  recourse  may  be  had  to  sodium  and  potassium, 
(kalium-natrium).  This  unique  mixture  of  metals  was  made  by  Dr. 
Emil  Schreier,  of  Vienna,  over  twenty-two  years  ago,  and  to  those  who 
have  learned  its  merit,  it  is  unquestionably  the  most  valuable  means 
at  our  disposal  in  root-canal  therapy.  It  has  an  intense  affinity  for 
water,  and  as  a  result  unites  with  any  form  of  organic  matter  with 
such  great  avidity  as  to  produce  immediate  oxidation  of  everything 
connected  with  the  union.  Thus,  a  given  quantity  of  sodium  and  potas- 
sium imites  with  a  given  quantity  of  organic  tissue,  and  the  result  is 
complete  destruction  of  that  much  organic  matter.  Only  a  portion 
as  large  as  a  pin-head  should  be  introduced  at  one  time,  on  account  of 
the  violent  reaction  which  takes  place.  In  the  case  of  a  putrescent 
canal,  as  soon  as  a  point  has  been  reached  where  there  is  the  slightest 
danger  of  forcing  infection  tlirough  a  foramen,  instrumentation  ceases, 
and  sodium  and  potassium  is  utilized.  On  the  end  of  a  barbed  broach 
a  very  small  quantity  of  the  medication  is  introduced  into  the  canal. 
The  result  is  flame,  smoke  and  gas,  and  when  this  has  subsided  we 
introduce  another  particle^  our  broach  constantly  passing  nearer  the 
end  of  the  root,  until  finally  ever}-  particle  of  putrescent  matter  has 
disappeared,  and  the  broach  has  passed  through  the  foramen.  Properly 
carried  out,  one  need  not  fear,  with  this  technic,  that  septic  matter 
may  be  forced  through  the  foramen,  and  when  irritation  results,  which 
rarely  occurs,  it  will  subside  within  from  twenty-four  to  forty-eight 
hours. 

In  the  removal  of  living  pulp  tissue,  the  sodium  and  potassium 
unites  and  destroys  all  of  the  immerous  shreds  of  organic  matter  that 
are  found  at  the  orifices  of  the  dental  tu])uli.  This  destruction  proceeds 
some  distance  into  the  tubuli.  Only  when  all  chemical  action  has 
ceased,  and  the  broach  has  passed  through  the  foramen,  can  it  be  said 
that  the  canal  is  void  of  organic  tissue.  In  the  removal  of  living  pulp, 
this  result  is  never  i)ossiblc  until  the  second  or  third  sitting.  There 
is  then  no  longer  any  anesthetic  condition,  l)ut  generally  some  sensa- 
tion remains  until  the  last  particle  of  ]:)ulp  has  been  removed,  when 
what  is  left  of  the  medication  becomes  inert  in  the  canal. 

The  greatest  value  of  this  material  is  found  in  chemically  reaming 
such  canals  as  appear  impossible  to  penetrate  on  account  of  })eing 
occluded  with  calcified  matter.    In  all  such  cases  some  organic  matter 


PP.RWEMENTAL  ABSCESS  283 

is  always  present  even  if  it  is  not  perceptiljle  to  the  naked  eye.  As 
long  as  the  slightest  moisture  is  left,  the  kalium-natrium  will  destroy 
this  stratum  of  tissue.  When  at  times  the  kalium-natrium  becomes 
inert  on  account  of  the  absence  of  moisture,  it  is  necessary  to  moisten 
the  canal  with  a  few  drops  of  distilled  water.  After  some  progress  has 
been  made  in  blazing  a  path  in  the  canal,  a  fine,  sharp-pointed  instru- 
ment, made  of  superior  hard-tempered  steel,  is  introduced  into  the  fine 
opening.  These  instruments  are  called  dental  picks,  and  with  the 
organic  strata  removed,  it  is  not  difficult  to  break  up  the  calicified 
mass  into  very  fine  fragments,  which  cling  to  the  picks  and  are  readily 
removed  when  fresh  sodium  and  potassium  is  introduced.  The  repe- 
tition of  this  technic  will  finally  succeed,  not  only  in  carrying  the  broach 
through  the  foramen,  but  also  in  widening  the  canal  sufficiently  to 
make  it  readily  accessible  to  the  canal  plugger.  Often  it  is  impossible 
to  pass  the  broach  through  all  the  foramina  until  the  patient  has  had 
a  mnnber  of  sittings. 

The  operation  can  cease  at  any  point.  The  use  of  sodium  and  potas- 
sium has  rendered  the  canal  aseptic  and  no  medicament  of  an}'  kind 
should  be  placed  in  the  canal.  The 
general  practice  of  sealing  in  the  canal 
some  •  antiseptic  remedy  cannot  be  too 
strongly  discouraged.  If  there  is  any 
abnormal  pathological  condition  at  the 
apex,  it  will  usually  be  obscured  by  the 
drug.  Then,  again,  it  interferes  with 
that  absolute  cleanliness  of  root  struc- 
ture which  the  operator  is  exerting 
every  energy  to  attain.    When  ready 

,       !•        •        ,1  ,"       ,  n  1  ]        •  '  FiG-     121.  —  Roentgenogram 

to  dismiss  the  patient,  a  fine  gold  wire      ^^^^^,.^^  ^.^i^  ^,.^^^  ^^^^.^^^^^  ^^e 
should  be  passed  up  the  canal  as  far  as       foramina. 
possible  through  the  foramen,  when  this 

can  be  done.  The  external  end  of  the  wire  is  then  bent  so  as  to 
make  it  easily  removable.  A  small  dressing  of  sterile  Japanese  paper 
or  cotton  is  now  packed  around  the  wire  to  prevent  the  ingress  of 
filling  materials,  and  the  cavity  is  sealed  with  base  plate  gutta-percha. 
The  tooth  is  then  radiographed  and  the  picture  discloses  whether 
the  wires  have  passed  through  the  foramina,  and  if  not,  how  far  they 
are  from  the  root  end  (Fig.  121).  Not  infrequently  it  will  be  found 
necessary  to  cut  away  more  tooth  structure  in  order  to  permit  the 
broach  to  enter  at  the  correct  point,  which  the  gold  wire  now  for  the 
first  time  discloses. 

These  wires  become  most  valuable  for  diagnostic  purposes  in  teeth 
having  pulp  nodules  and  canals  impacted  with  calcified  matter. 

A  stage  has  now  been  reached  where  it  can  be  consistently  said  that 
the  canals  are  clean.  The  roentgenogram  shows  the  wires  through 
every  canal  foramen.  The  canals  are  now  washed  out  with  a  solution  of 
1  part  of  sublimate  to  500  parts  of  hydrogen  peroxide  (Marchand  or 


284  ODONTALGIA   AND  ALVEOLAR  ABSCESS 

similar).  This  solution,  after  the  canals  are  dried,  will  leave  traces 
of  sublimate  along  the  orifices  of  the  tubuli. 

If  there  is  any  diseased  area  in  the  peri-apical  region,  it  has  not  up 
to  this  time  been  disturbed,  but  is  now  ready  for  extirpation.  The 
canals  are  now  flooded  with  physiological  salt  solution.  The  negative 
pole  of  a  galvanic  rheostat,  properly  constructed  for  this  purpose,  is 
now  attached  to  some  part  of  the  cheek  by  means  of  a  wet  sponge 
(Fig.  122).  The  positive  pole  consists  of  a  wire  of  chemically  pure 
zinc,  which  is  held  in  the  different  canals  in  turn.  Care  must  be 
taken  not  to  allow  the  zinc  point  to  pass  through  the  foramen  or  to 
occlude  the  opening,  so  that  it  may  not  interfere  with  the  egress  of 
gases  (emanating  from  the  peri-apical  area  when  the  granuloma  or  other 
form  of  pathogenic  tissue  is  being  destroyed)  through  the  tooth.  These 
rheostats  are  worked  by  a  shunt  system,  so  that  the  amperage  can 
be  gradually  increased  without  causing  any  discomfort.  One  or  two 
milliamperes  of  current  is  generally  easily  borne,  and  the  anode  should 
remain  in  each  canal  from  five  to  twenty  minutes. 

In  this  manner  ions  of  electricity,  together  with  nascent  chloride  of 
zinc,  are  forced  through  the  foramina.  The  tubuli  themselves  are  thus 
placed  in  an  absolutely  germicidal  state.  Any  ordinary  granuloma 
can  be  entirely  obliterated  in  this  way,  to  be  followed  by  the  growth  of 
new  alveolar  structure  if  no  place  is  left  for  any  invading  bacteria. 
When,  however,  the  cementum  of  the  root  itself  has  become  necrosed, 
apicoectomy  must  be  resorted  to  after  the  root  filling  has  been 
completed. 

The  root  canals  are  now  ready  for  filling.  The  first  essential  for  the 
root  filling  is  that  it  should  be  easily  forced  through  the  foramen; 
it  should  be  most  compatible  to  the  dental  structures,  indestructable 
and  void  of  any  irritating  properties.  As  long  as  the  filling  material 
fails  to  encapsulate  the  outside  of  the  end  of  the  root  it  is  inviting 
reinfection. 

Paraffin  always  presents  the  possibility  of  becoming  absorbed,  and 
is  therefore  contra-indicated.  Cements  composed  of  oxy chloride  of 
zinc,  or  containing  any  irritating  substance  like  formaldehyde,  are  con- 
tra-indicated. No  cement  substance  can  be  depended  upon  to  fill 
compactly  every  crevice  and  deflection  of  the  normal  canal,  to  say 
nothing  of  the  miniature  foramina  that  are  found.  The  frequent 
discovery  of  foramina  on  the  side  of  the  root  makes  it  essential  that  the 
canal  should  be  filled  with  a  solid  homogeneous  mass,  unchangeable 
in  its  nature,  and  which  will  hermetically  seal  the  mouth  of  every 
dentinal  tubule. 

Gutta-percha  meets  the  requirements  of  an  ideal  root  filling  better 
than  any  other  material.  Points  made  from  base  plate  gutta-percha 
are  selected  of  a  diameter  which  will  enable  them  to  go  to  the  end  of 
the  canal.  They  are  placed  in  a  10  per  cent,  solution  of  formalin,  so 
that  their  surfaces  will  be  aseptic.  The  canals  are  thoroughly  dried 
with  warm  air.    A  fine  broach,  upon  which  are  twisted  a  few  fibers  of 


PERICEMENTAL  ABSCESS 


285 


cotton,  is  dipped  in  a  very  liquid  solution  of  chlora-percha;  this  is 
carried  to  the  very  ends  of  the  canals.     With  an  aseptic  pair  of  tweezers 


Fig.  122. — Specially  designed  rheostat. 


286 


ODONTALGIA   AND  ALVEOLAR  ABSCESS 


the  gutta-percha  point  is  taken  from  its  bath,  is  carefully  dried  in  an 
aseptic  napkin  and  gently  carried  into  the  canal.  A  plugger,  which 
will  pass  to  the  end  of  the  canal,  is  dipped  into  alcohol,  ignited  at  a 
lamp,  and  the  warm  plugger  firmly  but  delicately  forces  the  gutta- 
percha point  to  the  end  of  the  canal.  One  or  two  more  fine  gutta- 
percha points  are  introduced  in  this  manner.  A  small  piece  of  Japanese 
paper  is  then  twisted  around  the  plugger;  this  is  soaked  in  chloro- 


FiG.  123. — Roentgenogram  showing  end  of  roots  encapsulated  with  gutta-percha  root 

fillings. 

form,  then  passed  into  the  canal,  and  the  gutta-percha  repeatedly 
packed  with  this  chloroform  tampon.  This  causes  the  gutta-percha  to 
become  soft  and,  under  pressure,  makes  it  pass  tlu-ough  the  foramina 
and  into  every  depression.  Fresh  gutta-percha  points  are  treated  in 
the  same  manner  until  the  filling  is  complete.  With  cold  air  every 
particle  of  chloroform  is  volatilized,  and  it  is  then  covered  with  an 
oxy chloride  of  zinc  cement  in  order  to  prevent  infection  tlirough  the 
crown. 


Fig.  124. — Roentgenogram  taken  two  years  after  aljscess  had  been  eradicated  by 
ionism.  It  shows  regenerated  alveolar  structure  and  protruding  gutta-percha  root 
filling  enmeshed  in  the  bone  cells. 


'ilie  tooth  is  now  again  radiographed  in  order  to  determine  if  the 
end  of  the  root  is  encapsulated  with  chlora-percha  (Fig.  123).  If 
the  root  filling  has  not  passed  through  the  end  of  the  root,  it  be- 
comes absolutely  necessary  to  remove  all  of  the  root  filling  and  again 
attemj)t  a  ccjrrect  filling.  ""J'he  final  roentgenogram  is  essential  in 
determining  whether  the  tooth  has  been  left  safe  from  the  possibility 
of  reinfection.    When  this  procedure  has  been  correctly  carried  out, 


PERICEMENTAL  ABSCESS  287 

there  can  be  no  possibility  of  reinfection,  and  in  time  new  alveolar 
structure  will  be  found  in  the  peri-apical  region,  as  is  shown  in  Fig. 
124. 

There  remains  one  class  of  cases  in  which  it  is  impossible  to  eradi- 
cate the  pathological  condition  by  means  of  ionism.  Whenever  any 
part  of  the  cementum  of  the  root  is  necrosed,  surgical  interference 
becomes  imperative.  Usually  nothing  short  of  root  amputation  will 
absolutely  cure  these  cases.  Unfortunately  it  is  not  always  possible 
in  the  reading  of  the  roentgenogram  to  know  whether  or  not  the  root 
surface  is  necrosed. 

The  great  advantage  in  being  able  to  cure  such  a  large  number  of 
peri-apical  infections  by  ionism  makes  it  better  practice  to  try  ionism 
in  all  doubtful  cases.  When  this  has  failed,  root  amputation  takes 
its  place  as  the  correct  procedure.  It  must,  however,  be  understood 
that  like  all  other  measures,  it  must  be  applied  in  such  a  manner  that 
no  pathogenic  spot  remains.  Imperfect  surgical  operations  are,  like 
imperfect  root-canal  technic,  absolutely  valueless  to  the  patient. 


CHAPTER  XII. 
DENTAL  PROPHYLAXIS. 

By  ALFRED   C.  FONES,  D.D.S. 

THE  CELL. 

Ix  order  to  appreciate  health  it  is  necessary  to  be  famihar  with 
the  facts  concerning  the  individual  cell,  and  the  effect  of  various  influ- 
ences upon  the  unit  must  be  studied  before  an  understanding  can  be 
had  of  the  action  and  influence  upon  the  cells  in  the  aggregate.  If 
a  drop  of  water  is  taken  from  the  side  or  bottom  of  an  aquarium  and 
put  in  a  glass  under  the  microscope,  a  minute  jelly-like  mass  may  be 
seen.  Its  outer  circumference  slowly  changes  its  shape,  while  near  the 
center  there  is  a  very  minute  globule  termed  the  nucleus.  This  is 
the  lowest  and  simplest  form  of  animal  life  and  is  known  as  the  ameba. 
This  simple  cell  has  seven  distinct  properties.  It  may  extend  its 
wall  in  projections  like  false  feet  or  protuberances  or  may  flatten 
itself  out  in  a  long  line,  therefore  it  has  the  property  of  elongation. 
When  irritated  by  being  brought  into  contact  with  dilute  acid  it  will 
contract  into  a  round  form;  hence,  it  has  the  property  of  contraction. 
These  two  properties  give  it  its  power  of  motion.  It  appreciates  the 
presence  of  irritants,  of  food  and  of  thermal  changes,  therefore  it  has 
the  power  of  sensation.  It  can  digest  food  and  discard  waste  tissue, 
therefore  it  must  have  the  properties  of  secretion  and  elimination. 
The  cell  and  nucleus  have  the  power  of  dividing  themselves  in  two, 
thereby  forming  two  cells.  It  has  the  power  of  reproduction,  and  the 
new  cells  have  the  property  of  gro^^i:h. 

When  all  of  these  functions  or  properties  of  this  simple  cell  are  work- 
ing normally,  the  ameba  is  in  a  state  of  health  or  balance.  Rob  it 
of  one  or  more  of  its  properties  and  it  is  diseased.  Stimulate  the  cell 
by  applying  certain  agencies  and  its  motions  become  more  rapid,  it 
consumes  its  food  more  rapidly,  it  will  subdivide  and  reproduce 
itself  more  rapidly.  A  greater  stimulant  will  cause  a  still  greater  activ- 
ity', but  if  this  is  continued  the  cell  soon  becomes  exhausted  and  par- 
alyzed from  exertion  and  the  ultimate  result  will  be  death.  The  reverse 
takes  place  under  sedation  produced  by  applying  cold.  The  motions 
become  slower,  also  digestion  and  reproduction.  If  the  temperature 
is  dropped  too  low,  the  cell  dies.  Pollute  the  water  or  rob  it  of  its 
oxygen  and  the  cell  dies.  Cell  life  is  maintained  chiefly  by  a  chemical 
process  of  oxidation.  It  must  have  water  and  it  must  have  a  food  sup- 
ply to  replace  the  lost  substance  which  is  gradually  being  utilized 


THE  CELL  289 

in  performing  its  various  properties  and  functions.  It  is  therefore 
apparent  that  cell  life  is  dependent  upon  oxygen,  water  and  food, 
a  proper  temperature  and  removal  of  waste  matter. 

Nature,  in  the  building  of  all  matter,  builds  from  the  unit.  Although 
the  atom  is  the  smallest  unit,  the  molecule  of  the  mineral  kingdom  and 
the  cell  of  the  animal  and  vegetable  kingdoms  are  the  general  bases 
for  study.  All  earthly  creations  visible  to  us  are  formed  on  this  one 
plan.  The  trees,  the  flowers,  the  grass,  the  mountains,  the  beach, 
the  sea,  all  animal  life,  including  man,  each  is  made  by  the  combining 
of  these  units,  all  working  with  an  intelligence  and  subject  to  chemical 
laws  far  beyond  our  comprehension. 

Why  it  is  that  the  contents  of  the  cell,  which  is  called  protoplasm 
and  which  appears  to  be  nothing  but  a  jelly-like  mass,  has  the  property 
of  manifesting  life  and  intelligence,  is  difficult  to  understand.  This 
substance  can  be  analyzed  and  even  the  proportion  of  its  elements 
estimated,  yet  what  unseen  force  imbues  it  with  energy  and  intelli- 
gence and  what  becomes  of  this  life-giving  power  when  the  cell  dies 
and  disintegrates,  is  not  known.  Cell  action  can  be  studied,  and  the 
cell  can  be  supplied  with  the  essentials  for  growth  and  development.  It 
is  a  realized  science  that  in  animal  life,  certain  factors  properly  applied 
at  the  proper  age  can  greatly  develop  its  function  and  intelligence, 
the  same  as  in  vegetable  life,  but  it  cannot  be  explained.  It  is  known 
that  all  manifestation  of  life  and  of  intelligence  is  expressed  through 
this  matter  contained  within  the  cell. 

In  the  gradual  evolution  of  these  simple  cells  like  the  ameba,  com- 
bining to  form  larger  and  more  complex  organisms,  it  is  fovmd  that 
the  cells  choose  a  specialty  of  two  or  three  of  these  properties,  and  those 
whose  specialty  is  the  same  are  grouped  together.  As  animal  life 
develops  into  higher  planes  the  cells  become  more  proficient  in  their 
specialties,  until  in  man  is  found  the  greatest  variety-  of  highly  special- 
ized cells  in  animal  life.  While  the  ameba  possesses  a  balance  of  seven 
properties,  some  of  the  specialized  cells  of  man  concentrate  on  but  one 
function.  It  may  now  be  seen  how  these  cells  of  man  that  have  under- 
gone a  slow  evolution  of  millions  of  years  to  reach  theii*  present  degree 
of  intelligence  are  reflected  in  this  low  and  simple  order  of  life — the 
ameba.  It  has  been  stated  that  the  ameba  has  seven  properties.  Its 
power  of  contraction  is  exemplified  in  the  muscle  cells  of  the  human 
body,  whose  specialty  is  contraction.  These  cells  are  capable  of 
wonderful  development  and  training.  The  finger  touch  on  the  piano 
keys,  the  surgeon  with  his  instruments,  the  dancer,  the  juggler,  the 
athlete,  the  artist,  and  the  artisan,  all  demonstrate  how  these  minute 
individuals  receive  impressions  from  the  brain  and  nerve  centers  and 
interpret  them  with  such  wonderful  intelligence.  The  nerve  cells 
specialize  on  the  transmission  of  sensation  and  vibratory  influences  to 
and  from  the  brain.  Digestion  and  elimination,  being  very  much  more 
complicated  in  higher  animal  life,  require  innumerable  cells  which 
perform  separate  functions — the  passing  on  of  food,  the  secretion  of 
19 


290  DENTAL  PROPHYLAXIS 

fluid  for  its  solution  and  its  preparation  for  absorption.  In  the 
blood  stream  are  cells  floating  along,  each  intent  on  its  special  duty. 
The  liver,  with  its  cells  actively  engaged  in  preparing  the  waste  pro- 
ducts for  elimination  by  the  kidneys,  the  sweat  glands,  the  lungs, 
the  brain  (that  wonderful  terminal  station,  headquarters  for  all  orders), 
all  are  composed  of  these  specialized  units  working  together  like  so 
many  people  in  an  immense  city,  each  adding  his  mite  in  labor  and 
service  for  the  common  prosperity  and  health. 

The  intelligence  displayed  by  the  individual  cells  of  the  body  is 
the  marvel  of  scientific  investigators  in  physiology  and  pathology. 
jNIuch  is  yet  \\Tapped  in  mystery  and  many  years  will  pass  before  some 
of  the  deep  problems  of  nutrition  and  the  hard-fought  battles  waged 
against  disease  will  be  fully  understood. 

When  the  body  is  abused  this  abuse  is  imposed  upon  millions  of 
intelligent  beings  who  do  their  utmost  to  offset  ignorance  and  wilful 
acts  by  patiently  combating  the  impositions  and  trying  to  correct 
and  repair  the  damage  wrought.  In  early  youth  the  cells  are  in  abun- 
dance and  the  supporting  structures  are  but  partially  formed.  In 
adult  life  the  work  of  the  cell  is  completed,  and  the  intercellular  struc- 
ture is  in  predominance.  The  great  period  for  structure  building  and 
for  the  guidance  of  proper  cell  development,  physically  and  intellec- 
tually, by  applying  scientific  factors  to  properly  influence  this  result, 
is  from  infancy  to  twelve  years  of  age. 

As  a  spider  spins  his  web  so  do  these  minute  cells  create  tissue 
to  aid  them  in  their  work.  The  individual  reflects  the  composite 
texture  and  make-up  of  the  aggregate  cells  of  the  body,  and  the  period 
for  molding,  refining  and  advancing  this  cell  development  to  its  high- 
est plane  is  in  early  youth. 

Factors  for  Cell  Life. — ^The  scientific  factors  for  infiuence  are  numer- 
ous, but  there  are  a  few  that  stand  out  conspicuously.  First  of  all 
comes  pure  air,  for  cell  life  is  dependent  upon  constant  oxidation. 
Next  comes  a  proper  food  supply.  The  character  of  food  will  eventu- 
ally determine  the  character  of  the  cell,  and  as  the  body  is  physically 
composed  of  millions  of  cells,  the  food  supply  in  a  great  measure 
determines  the  character  of  the  individual.  This  is  exemplified  in  the 
glutton,  the  drunkard  or  the  savage.  What  is  eaten,  how  much  is  eaten, 
and  the  manner  in  which  it  is  eaten,  are  some  of  the  chief  factors  for 
health  balance.  The  question  of  food  values,  the  quantity  consumed 
and  the  importance  of  thorough  mastication  and  insalivation  should 
be  a  study  for  all  hygienists. 

Next  comes  cleanliness,  for  if  disease  is  to  be  prevented  clean  food, 
clean  water,  clean  mouths,  clean  bodies  and  clean  environments  are 
necessary.  Mental  attitude  is  another  powerful  factor  and  should 
have  fourth  j)lace.  Self-control,  oi)timism,  that  mental  poise  that  can 
discard  fear  and  worry,  that  holds  an  even  balance  under  varying 
circumstances  and  that  can  radiate  good  cheer  and  kindness  through 
their  health-giving   influences  to  every  cell  of  the  body,  are  elixirs 


THE  CELL  291 

iineqiiak'd  in  the  buildiujij  of  the  charaeter  as  well  as.  in  regulating  a 
perfect  balance  and  functioning  of  the  entire  system. 

Although  heredity,  too,  plays  a  strong  part,  yet  the  first  four  factors 
named  can  greatly  modify  the  inherited  disposition  of  the  cells  if  wisely 
applied.  When  we  speak  of  coarse  natures,  we  speak  of  an  imfortunate 
inheritance  of  a  type  of  cell  life  that  might  have  been  greatly  softened 
and  modified  in  childhood. 

Exercise  is  also  exceedingly  important,  for  rest  means  rust  even  in 
animal  tissue. 

If  man  lived  what  is  termed  a  "natural"  existence,  which  means, 
in  other  words,  an  outdoor  and  primitive  life,  with  simple  coarse 
foods  and  work  or  exercise  in  the  open  air,  which  develop  the  animal 
side,  there  would  be  but  little  need  of  the  physician  or  the  dentist. 
The  coarse  food  would  mechanically  clean  and  polish  the  teeth  by 
friction,  and  the  out-of-door  exercise  or  work  would  cause  an  enforced 
breathing  which  would  mean  a  greater  intake  of  oxygen  to  burn  up 
the  slag  and  waste  products  in  the  system.  But  this  so-called  natural 
existence  is  not  possible  to  70  per  cent,  of  the  people  of  the  present 
day.  Their  very  existence  depends  upon  their  work  or  artificial  life 
in  the  cities,  and  the  yearly  increase  in  numbers  in  the  cities  rather 
proves  the  preference  for  the  city  over  the  country.  Therefore  this 
health  problem  of  city  life  must  be  solved.  The  factors  which  are 
productive  of  health  in  the  animal  life  must  be  substituted  artificially. 
The  passing  generation  cries  that  children  are  being  brought  up  too 
much  by  the  teaching  of  science  and  the  book  instead  of  in  the  good 
old-fashioned  way  of  letting  nature  look  after  them.  Take,  for  ex- 
ample, the  wild  rose  of  the  field  that  depends  upon  sunshine  and  shade, 
warmth  and  moisture  and  proper  soil  for  its  growth.  Natiu-e  does  not 
and  cannot  always  supply  these  in  sufficient  degree  and  in  proper  bal- 
ance, and  although  the  flower  is  beautiful  it  cannot  be  compared  with 
the  beautiful  rose  that  the  horticulturist  can  grow  when  these  essen- 
tials are  scientifically  and  artificially  supplied.  In  the  hot-house  the 
correct  temperature  can  be  maintained,  moisture  in  sufficient  quan- 
tity supplied,  sunshine  and  shade  regulated  at  will  and  fertilizers 
essential  to  stimulate  growth  added  to  the  soil.  The  work  of  Burbank 
in  scientifically  handling  vegetable  life  is  well  known  and  our  modern 
methods  of  agriculture  and  fruit  raising.  The  w'onderful  feats  of  the 
horse,  hurdling,  running  and  trotting  are  due  in  great  measure  to  the 
scientific  training  by  man.  Many  instances  can  be  given  in  which 
nature  far  excels  her  natural  state  of  environments  if  the  essential 
factors  she  needs  are  supplied  artificially  and  scientifically^  in  sufficient 
abundance  and  degree. 

And  so  it  is  in  the  growth  and  development  of  the  city  child,  and 
even  in  that  of  the  adult.  If  the  proper  factors  for  health  can  be  scien- 
tifically administered,  it  is  possible  to  grow  children  as  far  superior  to 
those  of  the  present-day  average  in  the  public  schools  as  the  American 
Beauty  is  superior  to  the  wild  rose.  Man  has  had  his  progressive  period; 
woman  is  having  hers.    The  coming  one  belongs  to  the  children. 


292  DENTAL  PROPHYLAXIS 


THE  ALIMENTARY  TRACT. 


Before  confining  thought  and  attention  chiefly  to  the  teeth  and  their 
surrounding  tissues  and  considering  how  disease  may  be  prevented, 
a  few  simple  thoughts  regarding  the  body  must  be  presented,  that  it 
may  be  better  understood  how  important  a  part  the  mouth  plays  for 
health  or  for  disease.  There  is  no  better  way  of  doing  this,  perhaps, 
than  first  to  consider  a  country  with  its  many  people,  and  show  the 
factors  upon  which  it  is  dependent  for  health,  for  a  close  analogy  may 
be  drawTi  between  the  life  of  a  simple  cell,  the  individual  and  the  nation 
as  a  whole.  Egypt  is  the  best  for  illustrating  this  thought,  for  here  is 
found  a  strip  of  life  running  through  a  region  of  apparent  death. 
Suppose  a  piece  of  green  cloth,  six  inches  wide  and  a  hundred  feet  in 
length,  was  laid  on  the  sands  of  the  seashore,  running  straight  upon 
the  beach  from  the  water's  edge.  If  in  the  center  of  this  cloth  was  laid 
a  long  white  string  to  illustrate  the  river  Nile,  it  would  be  a  fair  repre- 
sentation of  Egypt.  The  Nile  runs  through  a  desert  and  the  water 
with  its  life-giving  power  has  created  a  living  body  close  to  its  borders. 
In  this  living  body  are  millions  of  people  who  are  dependent  upon  this 
alimentary  tract  or  river  for  their  existence.  Along  the  banks  may  be 
seen  the  water  buckets,  operated  by  the  natives  to  supply  their  fields 
and  gardens.  In  the  season  of  the  overflow  the  soil  is  soaked  with 
moisture,  the  crops  are  plentiful  and  there  is  ample  for  those  who  will 
work.  Canals  or  arteries  lead  from  the  river  bank  across  the  fields 
to  supply  life  and  growi:h  to  the  soil  that  would  be  desert  waste  with- 
out it.  If  it  were  possible  to  poison  the  source  of  the  Nile  so  that  its 
waters  carried  their  life-giving  properties  no  longer,  but  contained 
some  chemicals  that  were  destructive  to  plant  life,  or  sufficient  sewage 
to  poison  the  inhabitants,  Egypt  would  soon  cease  to  exist.  Just  in 
proportion  to  the  amount  of  poison  carried  down  the  river  would  the 
country  and  people  suffer  from  starvation  and  disease.  The  bodies 
of  all  animal  life  are  constructed  around  their  alimentary  tract.  The 
lowest  forms  of  cell  life  when  changing  to  a  higher  organism,  find  it 
essential  to  develop  first  a  mouth  and  digestive  tract,  for  the  intake 
of  food,  is  of  first  importance  with  all  material  life.  The  body  with 
its  millions  of  cells  is  dependent  upon  the  flow  of  nourishment  through 
the  alimentary  tract  and  as  the  individual  lives  and  feeds  so  will  his 
body  thrive  or  deteriorate.  The  mouth  is  the  vestibule  or  gateway  to 
the  whole  system.  All  the  nourishment  and  food  supply  to  the  body 
must  pass  through  this  one  portal.  The  placing  of  the  food  in  the 
mouth  is  a  voluntary  action  and  it  can  be  controlled  as  long  as  it 
remains  there,  but  the  moment  it  is  swallowed  it  is  beyond  voluntary 
control  and  is  sent  on  that  mysterious  journey  called  digestion,  absorp- 
tion and  assimilation. 

Assuming,  first,  that  the  food  eaten  is  clean  and  pure  and  above 
criticism,  and  enters  a  clean  mouth,  is  properly  masticated  and  swal- 
lowed, digestion  takes  place  normally,  provided  the  mental  attitude 


THE  ALIMENTARY  TRACT  293 

be  one  of  tranquility  during  this  period.  If  the  mind  is  excited  or 
irritated,  it  will  send  depressing  messages  throughout  the  body  and 
the  process  of  digestion  is  retarded  and  disturbed. 

Under  such  clean  conditions  the  normal  processes  of  digestion  can 
take  place  with  a  minimum  amount  of  effort  and  energy  being  expended 
by  the  tissues  in  their  work,  and  the  product  after  digestion  is  fit  for 
the  blood  stream  to  offer  to  the  cells  of  the  body  the  nourishment  they 
need  to  perform  properly  their  respective  functions.  But  the  reverse 
situation  exists  regarding  the  mouth.  The  food  may  be  clean  and  pure 
but  the  mouth  unclean. 

Decomposing  Food  Debris. — In  discussing  the  harmful  effects  of 
decomposing  food  in  the  mouth,  the  subject  cannot  be  better  presented 
than  by  giving  some  of  the  thoughts  of  Dr.  E.  C.  Kirk  from  a  paper 
read  by  him  in  Providence,  R.  I.,  October  16,  1900,  and  published  in 
the  Dental  Cosmos  in  May,  1901,  entitled  "Some  Considerations 
Relative  to  the  Infant  jNIouth." 

Regarding  the  artificial  feeding  of  infants  he  refers  to  the  training 
of  the  nurse  to  sterilize  the  milk  and  feeding  apparatus  in  order  that 
the  milk  shall  be  delivered  to  the  child's  stomach  free  from  bacteria 
"  which  when  present  in  the  food  supply  so  alter  its  composition  as  to 
reduce  its  nutritive  value  and,  what  is  still  more  important,  set  up 
decomposition  processes  within  the  alimentary  tract  of  the  infant 
which  are  direct  causes  of  irritation  and  disease  to  the  infant  organism." 

Great  care  having  been  taken  in  preparing  the  food  and  in  feeding, 
no  attention  was  paid  to  the  film  of  milk  left  in  the  mouth  after  feeding. 
It  is  apparent  that  if  fresh  milk  is  poured  into  a  bottle  that  has  con- 
tained sour  milk,  infection  of  the  fresh  milk  will  immediately  take 
place.  In  the  feeding  process  the  sterile  milk  passing  over  the  infected 
surface  caused  by  the  residue  of  the  last  feeding  at  once  infects  the 
milk. 

Dr.  Kirk  says,  "There  can  be  but  one  result;  fermentation  of  the 
infected  fluid  begins  in  the  stomach;  putrefaction  of  the  proteid  ele- 
ments may  take  place;  quantities  of  gas  are  formed,  distending  the 
walls  of  the  stomach  and  intestines,  causing  pain  and  irritation, 
further  increased  by  the  irritating  effects  of  organic  acids  ^\%ich  are 
end-products  of  this  fermentative  process.  Digestion  is  interfered  with 
or  arrested,  the  fermenting  mass  of  food  becomes  a  mechanical  as 
well  as  a  toxic  irritant ;  diarrhea  sets  in,  the  whole  nutritional  process  is 
interfered  with  and  development  is  damaged  in  proportion  to  the 
length  and  severity  of  the  attack. 

"  The  rational  remedy  for  this  state  of  affairs  is  clear  when  once  the 
conditions  to  be  therapeutically  met  are  understood.  In  the  first 
place,  removal  of  the  primal  cause  by  thorough  oral  cleanliness  and 
sterilization  in  so  far  as  that  end  may  be  obtainable.  This  may  be 
practically  accomplished  by  wiping  the  mucous  membrane  with  a 
saturated  solution  of  boric  acid  to  which  borax  has  been  added  in  the 
proportion  of  ten  grains  to  the  ounce,  or  with  a  very  dilute  solution 


294  DENTAL  PROPHYLAXIS 

of  phenol  sodiqiie,  one-half  dram  to  the  ounce,  applied  on  a  cotton 
swab  or  with  a  soft  linen  handkerchief  \ATapped  around  the  finger 
of  the  nurse." 

Now  apply  the  same  principle  to  the  growing  child  and  to  the  adult. 
The  teeth  of  a  child  between  the  ages  of  six  and  twelve  years  will 
present  surfaces  equal  to  twelve  to  sixteen  square  inches.  In  an  adult 
the  surfaces  wUl  average  about  twenty-five  square  inches.  This  means 
that  if  it  were  possible  to  peel  the  enamel  off  of  each  of  the  five  sur- 
faces of  each  tooth  and  place  them  side  by  side  they  would  cover  a 
piece  of  glass  three  and  one-half  inches  square  in  the  case  of  the  child, 
and  in  that  of  the  adult  a  piece  about  five  inches  square.  This  will 
give  a  rough  idea  of  the  amount  of  surface  presented  in  the  mouth  to 
permit  of  the  retention  of  a  certain  quantity  of  food  that  must  decom- 
pose unless  it  is  removed.  The  more  perfect  the  teeth  regarding 
form,  occlusion  and  enamel  surface,  the  more  self-cleansing  they  are, 
and  proportionately,  the  amount  of  food  so  retained  is  comparatively 
small.  The  mouths  that  present  such  ideal  conditions  are  rare,  espe- 
cially among  those  who  are  born  and  live  in  the  cities.  Where  the  teeth 
are  irregular  in  shape  and  position,  are  decayed  and  broken  down,  the 
amount  of  food  that  remains  is  considerable  and  the  volume  of  decom- 
posing material  constantly  being  swept  mto  the  intestinal  tract  will 
eventually  breed  illness.  In  a  growing  child  such  mouth  conditions 
are  vicious.  "Suppose,"  said  a  prominent  educator  in  dentistry, 
"that  a  prescription  was  given  to  a  mother  by  a  physician,  to  mix, 
with  each  meal  that  the  child  ate,  a  half-spoonful  of  garbage.  Would 
she  carry  out  such  a  prescription,  and  if  she  did  and  the  child  became 
ill,  would  not  the  physician  be  liable  for  damages?"  And  yet  in  reality 
that  is  what  is  taking  place  in  the  average* mouth  of  the  children  in 
our  public  schools  and  in  the  mouths  of  the  great  working  classes. 
This  constant  drain  of  poison  into  the  intestinal  tract  in  child  life 
causes  an  intestinal  indigestion  where  bacterial  products  are  absorbed 
into  the  system  and  produce  fevers,  headaches,  eye-strain,  anemia, 
malaise,  constipation,  and  dizziness,  Nature  finally  takes  away  the 
child's  appetite  and  forces  it  to  bed  until  a  good  house-cleaning  of  the 
body  can  be  accomplished. 

These  poisons  from  the  mouth  are  insidious  and  slow  in  action. 
Many  can  and  do  withstand  them  for  years,  but  as  the  constant  drop- 
ping of  water  will  wear  away  the  stone,  so  will  the  products  of  decom- 
posing food  in  the  mouth  soon  destroy  good  digestion  and  undermine 
the  system. 

Vaughn  and  Novy,  in  their  book  entitled  Cellular  Toxins,  say, 
"The  effect  of  a  chemical  compound  upon  the  animal  body  depends 
upon  the  conditions  under  which  and  the  time  during  which  it  is  admin- 
istered. Thirty  grains  of  quinine  may  be  taken  ))y  a  healthy  man  (hir- 
ing twcnt.y-hnir  hours  without  any  apprecial>le  ill-effect,  yet  few  would 
be  willing  to  admit  that  the  administration  of  this  amount  daily  for 
months  would  be  wise  or  altogether  free  from  injury.     In  the  same 


THE  ALIMENTARY  TRACT  295 

manner  the  administration  of  a  given  quantity  of  a  bacterial  alkaloid 
to  a  dog  or  a  guinea  pig  in  a  simple  dose  may  do  no  harm,  while  the 
daily  production  of  the  same  substance  in  the  intestine  of  a  man  and 
its  absorption,  continued  through  weeks,  and  possibly  years  may  be 
of  marked  detriment  to  the  health." 

It  must  be  borne  in  mind  that  the  manifestation  of  sickness  does 
not  come  from  the  presence  of  bacteria,  but  from  the  poisons  generated 
by  the  bacteria. 

"  Abbott  in  his  book  on  The  Principles  of  Bacteriology,  quotes  Roux 
and  Yersin  who  claim  that  the  potencies  of  the  poisons  that  have 
been  isolated  from  cultures  of  Bacillus  diphtheria  have  been  determined 
by  experiments  upon  animals,  and  it  has  been  found  that  0.4  milli- 
gram is  capable  of  killing  eight  guinea-pigs.  Please  remember  that 
four-tenths  of  a  milligram  represents  but  y^^j  part  of  a  grain.  Aside 
from  the  products  of  decomposing  food  in  unsanitary  mouths  we  must 
seriously  consider  how  much  of  the  bacterial  poisons  may  be  generated 
in  such  mouths  daily  by  the  millions  of  microorganisms  present,  and 
whether  these  poisons  are  not  of  sufficient  quantity  eventually  to 
weaken  the  organism  and  render  the  body  susceptible  to  infection 
from  the  pathological  group  of  microorganisms.  In  the  battle  being 
waged  against  tuberculosis,  this  feature  will  be  given  much  impor- 
tance and  the  day  is  not  far  distant  when  some  scientist  will  be  able  to 
compute  with  a  reasonable  degree  of  accuracy  how  much  bacterial 
poison  can  be  generated  in  twenty-four  hours  in  a  mouth  containing 
decayed  teeth  and  food  debris. 

Bacterial  Propagation. — In  considering  the  products  of  decomposing 
food  with  their  detrimental  action  on  the  system,  their  action  upon 
the  human  mouth,  than  which  there  is  no  better  breeding  ground  for 
germ  life,  must  also  be  considered.  The  mouth  is  an  ideal  incubator, 
for  here  we  find  all  of  the  essentials  for  the  propagation  and  develop- 
ment of  these  microorganisms.  The  right  temperature,  sufficient 
moistm-e,  air,  darkness  and  a  menu  to  choose  from  that  would  tempt 
any  member  of  this  large  family.  Germ  life  is  comparatively  harmless 
when  robbed  of  a  food  supply,  but  give  it  a  pabulum  upon  which  to 
feed,  develop  and  multiply,  and  it  becomes  active  and  virulent.  It 
must  be  borne  in  mind  that  all  mucus-lined  tracts  of  the  body  have 
their  flora  of  microorganisms  and  that  the  individual  must  live  among 
them,  that  the  few  friendly  ones  are  company,  but  that  too  many  are 
a  crowd,  and  that  in  this  crowd  are  our  enemies  who  feed  upon  the 
host  if  they  but  get  a  chance. 

An  unclean  mouth  means  an  increased  number  of  bacteria,  and 
with  increased  numbers  come  increased  dangers  from  infection.  The 
cavities  of  decayed  teeth  harbor  millions  of  these  mischief-makers, 
as  do  also  the  food  debris  and  calcareous  deposits  around  the  necks 
of  the  teeth.  They  may  enter  the  mouth  in  a  very  subdued  state, 
but  under  these  favorable  environments  they  soon  multiply  rapidly. 
The  usual  order  is  to  consider  their  activity  and  growth  in  unsani- 


296  DENTAL  PROPHYLAXIS 

tary  mouths,  but  this  will  be  reversed  and  the  medium  upon  which  they 
best  are  cultivated  in  the  laboratories  be  first  noted.  The  saprophytic 
class  are  those  which  exist  upon  dead  animal  or  vegetable  matter. 
The  parasitic  class  prefers  to  gather  its  nourishment  from  the  living 
host.  [Many  of  both  classes  can  live  in  either  medium,  as  occasion 
demands. 

As  the  unorganized  ferment  of  gastric  or  intestinal  digestion  has 
the  power  of  changing  the  food  by  rearranging  its  elements,  usually 
by  a  process  of  hydration,  so  do  these  microorganisms  have  the  power 
of  breaking  down  tissue  or  decomposing  food  and  liberating  its  ele- 
ments in  their  search  for  carbon  and  nitrogen.  The  media  chiefly 
used  in  laboratories  for  cultures  of  microorganisms  are  bouillon, 
gelatin,  agar-agar,  potato,  sugar  and  blood  serum.  If  these  are 
kept  at  the  right  temperature  at  least  to  grow  mixed  cultures,  the  sapro- 
phytic class  is  quite  easily  developed,  for  the  extracts  of  beef,  sugars 
or  starches  form  an  attractive  pabulum.  Many  of  the  parasitic  variety 
can  also  be  growTi  in  these  substances,  such  as  the  typhoid  bacillus, 
anthrax  and  others,  w^hile  the  tubercle  bacillus  and  the  bacillus  of 
diphtheria  are  cultivated  in  the  blood  serum.  These  culture  media 
with  the  exception  of  agar-agar,  are  all  found  in  the  average  mouth, 
even  to  the  blood  serum. 

When  the  teeth  are  decayed  the  amount  of  food  retained  in  the 
mouth  is  considerable,  but  especial  attention  should  be  called  to  con- 
gested and  bleeding  gums.  Here  is  an  ideal  medium  for  the  propa- 
gation of  infectious  germ  life,  and  it  is  not  only  the  cavities  in  the 
teeth  and  the  food  debris,  but  also  the  pernicious  condition  of  the  gum 
tissue  in  unsanitary  mouths,  especially  in  those  of  children,  that  is 
of  serious  concern.  The  germs  of  tuberculosis  or  of  diphtheria  can 
here  find  a  pabulum  for  their  propagation  and  development,  and 
undoubtedly  the  prevailing  condition  of  the  gingival  borders  of  the 
gums  is  one  of  the  most  important  steps  toward  infection.  The  bleed- 
ing and  congested  gums  and  the  decomposing  food  is  present,  all  that 
Ls  now  necessary  is  the  bacterium. 

All  observant  practitioners  will  readily  agree  to  the  statement  that 
mouths  that  contain  no  congested  areas  on  the  gingival  borders  of 
the  gums  are  exceptions.  The  dark  red  surfaces  will  bleed  upon  the 
slightest  pressure,  and  in  between  the  molars  and  bicuspids  where 
the  food  can  lodge  undisturbed  in  ill-kept  mouths,  even  a  slight  suc- 
tion will  start  a  copious  l)leeding.  It  will  be  the  privilege  of  the  hygien- 
ist  to  note  in  the  treatment  of  each  new  patient  how  easily  the  gums 
will  bleed  upon  the  slightest  touch  of  instrument  or  porte  polisher.  The 
oozing  of  serum  and  blood  from  these  congested  points  is  of  equal 
importance  in  the  consideration  of  infectious  diseases  of  children  as 
the  dec(jinposing  of  animal  and  vegetable  matter  found  in  the  decayed 
teeth  or  around  their  surfaces.  To  those  who  have  thoroughly  inves- 
tigated the  subject,  the  mouth  is  now  conceded  to  be  a  most  impor- 
tant field  for  bacterial  growth  and  systemic  infection. 


TUBERCULOSIS  297 

Tuberculosis, — One  of  the  greatest  battles  being  waged  in  preventive 
medicine  is  the  fight  against  tuberculosis,  and  this  fight  can  never  be 
won  as  long  as  the  mouth  conditions  of  the  mass  of  the  people  remain 
as  they  are  at  present. 

Examine  the  mouths  of  the  children  in  our  large  cities  who  leave 
school,  say,  at  fourteen  and  fifteen  years  of  age,  and  you  will  note  that 
at  least  oO  jier  cent,  of  them  have  lost  or  are  losing  their  molar  teeth 
through  decay.  At  the  very  start  of  their  lives,  then,  the  nutritional 
system  is  handicapped  by  the  lack  of  power  of  the  teeth  to  crush  prop- 
erly the  food  which  enters  the  alimentary  tract.  The  bolting  of  food 
becomes  a  habit,  the  stomach  is  daily  called  upon  to  dissolve  large 
particles,  which  means  that  the  blood  is  retained  in  the  stomach  much 
longer  than  otherwise  necessary,  the  glands  become  overworked  in 
secreting  sufficient  gastric  juice,  an  extra  supply  of  blood  is  maintained 
in  the  digestive  tract  longer  than  necessary,  and  this  means  a  lessened 
amount  of  energy  to  expend  in  physical  and  mental  work. 

As  to  young  women  employed  in  factories,  the  sedentary  life  only 
adds  to  the  weakening  of  the  vital  forces,  especially  if  the  ventilation 
is  poor  and  the  environments  depressing.  Add  to  this  the  lack  of  sani- 
tation found  in  such  mouths  and  we  can  understand  why  it  is  that 
housewives  rank  second  on  the  list  in  tubercular  sanitariums,  shop 
hands  exceeding  them  in  numbers  by  a  small  margin.  When  these 
women  marry  and  bear  children  their  forces  are  still  further  lowered 
until  their  resistive  forces  are  so  weakened  that  infection  is  a  very 
small  matter.  The  offspring  of  such  a  parent  must  necessarily  be  a 
weakling,  especially  in  youth,  and  its  tissues  most  susceptible  to  tuber- 
cular infection.  People  so  seriously  lacking  vigor,  life  and  good  spirits 
become  the  great  "sick"  class,  and  this  class  spells  but  one  word 
• — poverty. 

Much  stress  is  laid  upon  insufficient  quantity  and  poor  quality  of 
the  food  supply  as  a  great  causative  factor  in  this  disease.  This  con- 
dition is  brought  about  more  through  ignorance  than  because  of  lack 
of  funds  with  which  to  purchase  proper  food,  for  the  body  can  be  well 
nourished  daily  for  a  very  moderate  sum  if  judgment  and  knowledge 
are  used  in  the  buying. 

Scientific  investigators  are  now  agreed  that  tubercular  infection 
takes  place  through  the  intestinal  tract  much  more  frequenth'  than 
previously  surmised.  In  fact  many  pathologists  insist  that  this  is 
the  chief  path  of  infection.  If  this  is  true,  the  bacilli  must  either  be 
taken  in  with  the  food  supply  in  sufficient  quantities  to  prove  danger- 
ous, or  they  must  find  lodgement  in  the  mouth  in  decayed  teeth  or 
congested  gum  surfaces  where  they  become  numerous  and  aggressive. 
In  our  state  sanitariums  where  the  tubercular  patients  are  segregated, 
the  mouth  conditions  are  deplorable.  It  is  true  that  with  plenty  of 
fresh  air,  good  food  and  rest,  the  body  can  and  does  neutralize  much  of 
the  poison.  The  resistive  force  is  increased  and  the  disease  is  pro- 
nounced arrested.    The  word  cure  is  cautiously  used. 


298  DENTAL  PROPHYLAXIS 

Could  the  mouths  of  these  patients  be  made  sanitary  at  the 
beginning  of  the  treatment  and  rigid  rules  enforced  regarding  their 
daily  care,  a  marked  benefit  would  surely  be  observed. 

Systemic  Infection. — If  syphilis  and  wounds  of  the  surfaces  of  the 
body  are  excluded,  there  are  but  three  ways,  ordinarily,  for  bacteria 
to  gain  entrance  into  the  blood  stream:  (1)  through  tooth  passes, 
such  as  root  canals  and  diseased  peridental  membranes;  (2)  through 
the  tonsils,  and  (3)  through  the  intestines.  Infection  through  the 
tonsils  or  through  the  intestinal  tract  is  dependent  in  a  great  measure 
on  mouth  conditions.  If  unsanitary  or  septic  conditions  exist  in  the 
buccal  cavity,  many  bacteria  in  a  state  of  virulency  are  constantly 
drained  over  the  tonsils  and  into  the  stomach.  Any  physical  depres- 
sion that  lowers  the  normal  resistance  of  the  body,  might  permit  of  the 
invasion  of  these  pathogenic  organisms.  When  the  mouth  is  clean  and 
wholesome,  the  liability  to  this  form  of  infection  is  greatly  lessened. 
The  greatest  sources  of  systemic  infection  are  through  the  root  canals 
of  decayed  and  pulpless  teeth,  and  infected  peridental  membranes. 
A  streptococcus  may  be  non-pathogenic  and  non-hemolytic  in  the 
fluids  of  the  mouth,  yet,  if  ingress  be  found  through  the  root  canal  to 
the  apical  space,  the  character  of  the  organism  may  undergo  a  change 
and  become  pathogenic  in  its  new  environment.  Bathed  in  serum  and 
compelled  to  secure  nourishment  from  the  new  source,  it  may  develop 
the  power  of  dissolving  blood.  If  conditions  are  favorable  and  it  is 
swept  into  the  blood  stream  through  the  lymphatics,  or  if  it  pene- 
trates the  walls  of  the  capillaries,  its  lodgement  in  some  other 
tissue  or  organ  of  the  body  will  set  up  a  local  and  a  systemic  dis- 
turbance that  will  cause  a  serious  illness,  with  possible  death,  to  the 
individual. 

Pyorrhea  alveolaris  is  an  infection  of  the  peridental  membrane. 
Should  the  tooth  become  loosened  from  the  disease,  and  pus  exude 
from  the  socket,  the  play  of  the  tooth  up  and  down  in  its  socket  during 
mastication  acts  like  a  pump,  and  forces  the  bacteria  through  the  walls 
of  the  capillaries  into  the  blood  stream.  Another  short  period  of 
scientific  investigation  will  substantiate  the  fact  that  tooth  passes 
constitute  one  of  the  greatest  sources  of  systemic  infection. 

In  order  to  secure  all  possible  results  from  practising  mouth  hygiene, 
our  efforts  should  be  concentrated  upon  the  children  in  our  public 
schools.  Here  we  will  find  the  source  where  most  of  the  evils  of  adult 
life  have  their  origin,  and  not  until  this  work  is  started  and  seriously 
carried  on  in  our  public  schools  can  wc  hope  to  wi])e  out  infectious 
diseases,  or  preserve  the  teeth,  or  get  control  of  dental  decay  with  its 
attendant  ills. 

Seemingly  defective  eyesight  in  childhood  is  commonly  caused  by 
the  poisonous  ])roducts  of  mouth  iufcction  al)Sor})cd  from  the  alimen- 
tary tract.  What  seems  to  be  astigmatism  disapi)ears  when  decayed 
teeth  are  filled,  mouth  hygiene  practised,  and  the  digestive  tract 
cleaned  up. 


THE  PRINCIPLES  OF  DENTAL  PROPHYLAXIS  299 

Anemia  can  in  a  great  measure  be  traced  to  the  same  source,  and 
there  is  no  doubt  but  that  better  mouth  conditions  will  greatly  aid  the 
medical  inspectors  to  solve  this  problem, 

THE  PRINCIPLES  OF  DENTAL  PROPHYLAXIS. 

The  initial  cause  of  nearly  all  the  pathological  or  disease  con- 
ditions of  the  tissues  of  the  mouth  is  the  combination  of  microorgan- 
isms and  food  debris.  Bacteria  alone  or  food  debris  alone  would  be 
quite  harmless  in  the  mouth.  Nearly  all  germ  life,  in  order  to  become 
virulent,  or  its  presence  dangerous  or  even  objectionable,  must  have 
a  pabulum  upon  which  to  thrive.  It  is  therefore  dependent  upon 
some  attractive  food  supply  in  order  to  reproduce  and  multiply.  It 
is  known  that  foods  will  "spoil"  if  allowed  to  remain  in  a  warm  tem- 
perature for  any  length  of  time,  and  that  in  order  to  prevent  this  action 
the  germs  are  killed  by  boiling  or  heating  the  food,  tightly  sealing  it 
from  the  air  in  cans  or  jars  that  have  just  previously  been  boiled  or 
have  had  boiling  water  poured  into  them,  and  allowing  them  to  stand 
long  enough  for  their  surface  to  become  sterilized. 

Food  may  also  be  placed  where  it  will  be  kept  cold,  as  in  an  ice-box, 
where  the  presence  of  the  ice  will  so  reduce  the  temperature  that  the 
organisms  are  rendered  sluggish  and  inert. 

For  years,  many  efforts  have  been  made  to  find  some  drug  or  chemical 
that  could  be  used  in  the  mouth  to  kill  all  bacteria,  and  thus  make  the 
mouth  sterile,  or  at  least  to  render  them  inert.  The  futility  of  even 
hoping  for  a  sterile  condition  of  the  mouth  has  long  since  been  demon- 
strated. It  is  impossible  to  sterilize  the  human  mouth,  and  even  if 
it  were  possible,  such  a  condition  could  be  maintained  but  a  very 
short  time.  Therefore,  if  it  is  impossible  to  keep  the  mouth  free  from 
bacterial  life,  and  as  the  combination  of  food  debris  and  bacteria  is 
the  chief  cause  of  dental  diseases,  is  there  not  some  way  in  which  the 
food  debris  can  be  thoroughly  removed?  It  is  upon  this  thought  that 
the  principles  of  prophylaxis  are  based. 

Dental  prophylaxis  is  that  scientific  effort,  either  operative  or  thera- 
peutic, tchich  tends  to  prevent  diseases  of  the  teeth  and  their  surrounding 
tissues.  Correcting  and  restoring  to  normal  function  all  abnormal 
or  pathological  conditions  of  the  teeth,  and  maintaining  that  normal 
condition,  is  a  prophylactic  procedure.  This  includes  practically  all 
the  operations  in  dentistry.  The  mere  filling  of  a  tooth  cannot  be 
termed  prophylactic  unless  the  operation  is  performed  with  a  knowl- 
edge and  skill  that  tends  to  prevent  future  decay  at  that  point  and 
that  will  restore  the  surface  of  the  tooth  to  normal  contour  and  normal 
function.  Crowns  and  bridges,  root-fillings,  approximal  fillings  with 
proper  contact  points,  and  smooth,  flush  margins,  the  correction  of 
malocclusion,  the  removal  of  all  calcareous  deposits,  polishing,  the 
insti-uction  in  the  proper  home  care  of  the  mouth,  may  all  be  made 
prophylactic  if  properly  done. 


300  DENTAL  PROPHYLAXIS 

Field  of  Service. — The  exposed  surfaces  of  the  teeth,  the  necks  of  the 
teeth  directly  under  the  free  margin  of  the  gums,  and  the  gum  tissue 
itseh',  are  the  parts  of  most  concern  to  the  dental  hygienist.  Bearing 
in  mind  that  from  now  on  the  battle  is  to  be  one  of  extreme  cleanliness 
on  the  one  hand,  and  on  the  other  an  effort  to  starve  and  render  inert 
the  bacteria,  the  mouth  of  the  average  adult  may  now  be  examined. 
It  is  first  noted  that  the  enamel  is  without  luster  and  covered  with  a 
pasty  and  colorless  film.  The  necks  of  the  teeth  are  stained;  calcare- 
ous deposits  are  seen  on  the  inside  surfaces  of  the  lower  incisors  and 
also  on  the  buccal  surfaces  of  the  upper  molars ;  if  there  are  gold  fillings, 
they  are  tarnished  and  spotted  with  dark  stains;  other  fillings  in  the 
teeth  are  rough  and  the  margins  are  extended  beyond  the  tooth  surface 
so  that  the}^  hold  particles  of  food  debris.  The  gums  are  quite  a  deep 
red  in  color,  especially  upon  the  gingival  borders,  and  if  they  are 
pressed  upon  even  lightly  by  an  instrument  they  will  bleed.  Between 
the  teeth  may  be  seen  food  debris,  and  at  these  points  the  gums  will 
bleed  copiously  if  wounded.  Even  if  there  are  no  decayed  surfaces  of 
the  teeth,  although  the  chances  are  there  are  many,  the  whole  mouth 
presents  an  unsanitary  condition  that  means  a  breeding-ground  for  mil- 
lions of  microorganisms  and  a  menace  to  the  health  of  the  individual. 
It  must  be  borne  in  mind  that  these  people  should  not  be  censured 
for  this  condition  of  their  mouths,  for  the  chances  are  they  have  never 
been  trained  or  taught  how  to  care  for  them  properly.  No  one  has 
taught  them  how  to  use  the  tooth-brush  or  the  floss.  No  one  has  been 
careful  to  see  that  the  fillings  were  smooth  and  polished  so  that  they 
would  not  retain  food.  Nor  have  they  been  taught  the  necessity  of 
brushing  their  gums  or  been  advised  as  to  how  the  mouth  should  be 
properly  taken  care  of.  So  it  is  the  duty  of  the  hygienist  to  be  kind 
in  her  criticism  to  these  patients,  and  it  w411  be  found  that  the  great 
majority  of  them  will  be  only  too  glad  to  reform  and  faithfully  follow 
instructions  W'hen  they  are  once  enlightened.  The  dental  hygienists 
are  to  be  the  educators,  to  spread  the  gospel  of  cleanliness,  and  to  aid 
both  children  and  adults  to  keep  well.  Many  times  mouths  will  be 
found  that  are  not  as  they  should  be;  some  may  be  quite  shocking  in 
fact,  but  it  must  be  remembered  that  the  chief  mission  is  to  treat 
and  help  others  to  know  how  to  keep  well,  and  after  these  unsanitary 
mouths  have  been  seen  to  grow  and  develop  into  healthy  ones  under 
prophylactic  skill  and  instruction,  it  will  be  realized  that  the  service 
of  the  hygienist  to  humanity  is  a  very  important  one. 

Analyze  one  of  these  unsanitary  mouths  and  study  the  conditions 
that  are  present.  If  the  mouth  contains  alloy  fillings  the  surfaces 
should  be  examined  and  also  the  margins  of  the  fillings  to  see  if  they 
are  rough.  If  so,  the  dentist  must  carefully  grind  and  polish  them  in 
order  that  the  results  which  may  be  expected  from  prophylaxis  may 
be  secured.  If  these  alloy  fillings  are  in  the  approximal  surfaces  of 
the  teeth  and  the  space  between  them  is  sufficiently  large  to  permit 
the  food  to  be  squeezed  down  between  the  teeth  and  to  injure  or  inflame 


THE  PRINCIPLES  OF  DENTAL  PROPHYLAXIS  301 

the  gum  tissue,  then  the  dentist  should  aid  the  hygienist  by  removing 
these  fillings  and  replacing  them  with  smoothly  finished  ones  having 
proper  contact  points  that  will  prevent  the  food  from  getting  between 
the  teeth.  If  there  are  gold  crowns  or  banded  crowns  that  do  not  fit 
tightly  to  the  tooth  or  root  and  that  will  permit  the  end  of  the  explorer 
to  pass  up  between  the  root  and  the  band  or  crown,  it  may  be  taken 
for  granted  that  such  a  space  is  filled  with  decomposing  food  and  is 
an  ideal  haven  for  bacteria.  The  odor  arising  from  such  crowTis  after 
their  removal  makes  one  realize  the  necessity  for  tight-fitting  bands 
and  flush  joint  operations.  Hygienists  will  come  to  loathe  the  average 
gold  crown  and  will  use  their  influence  against  their  insertion.  ]\Iany 
of  them  are  sources  of  systemic  infection  and  nearly  all  will  destroy 
the  peridental  membrane  around  the  tooth,  and  result  in  the  event- 
ual loss  of  the  tooth.  Such  dentistry  is  a  serious  menace  to  public 
health  and  has  undoubtedly  been  the  cause  of  many  severe  illnesses 
that  have  resulted  even  in  death.  If  an  ill-fitting  gold  crown  is  placed 
over  a  tooth  containing  a  live  pulp,  it  is  but  a  question  of  time  when 
the  bacteria  and  the  poisons  generated  b}'  the  decomposing  process 
of  the  food  debris  lodging  in  the  space  under  the  crowns  where  the 
cement  has  disintegrated  and  washed  away,  will  penetrate  the  dentin 
and  infect  and  destroy  the  pulp.  Alveolar  abscesses  from  teeth  carry- 
ing gold  crowns  are  common.  It  would  be  far  better  for  the  patient 
who  could  not  afford  to  have  the  work  done  properly,  to  have  such 
teeth  extracted.  Ill-fitting  bridges  so  constructed  that  it  is  impossible 
to  properly  remove  the  food  with  the  brush  and  washes,  will  badly 
hamper  work  for  mouth  hygiene. 

It  is  not  necessary  to  know  the  details  of  the  work  of  construction 
of  crowns  or  bridges  or  of  fillings,  but  it  is  necessary  to  know  what 
constitutes  good  dentistry  and  sanitary  construction.  A  small  pimple 
on  the  gum,  termed  by  the  layman  gum-boil,  is  in  reality  a  fistula 
opening  from  an  alveolar  abscess.  The  attention  of  the  dentist  should 
be  called  to  these  fistulse  so  that  he  may  open  the  root  canals  and  cure 
the  abscess. 

The  gum  tissue  should  now  be  examined.  The  term  congested  gums 
is  applied  to  enlarged  capillaries,  engorged  with  blood  and  having 
a  sluggish  circulation.  External  irritation  from  lack  of  use  and  func- 
tion in  the  mastication  of  proper  foods  is  usually  the  cause  for  this 
congestion.  The  deep  red  color  is  due  chiefly  to  the  sluggish  flow  of 
blood  laden  with  carbon  dioxid.  Perfect  metabolism  is  not  taking 
place  in  the  cells  of  this  tissue  and  the  waste  products  are  not  being 
carried  away  with  sufficient  rapidity.  Any  local  irritant  on  the  sur- 
face or  border  of  the  gums  will  produce  this  congestion,  and  the  mouths 
are  rare  that  do  not  contain  a  number  of  congested  surfaces. 

In  children  this  condition  is  produced  chiefly  by  the  sharp  edges 
of  decayed  or  broken-down  teeth,  temporary  and  permanent,  and 
sufficient  blood  and  serum  ooze  from  these  blood-engorged  surfaces 
to  form  an  excellent  culture  medium  for  pathogenic  bacteria.     The 


302  DENTAL  PROPHYLAXIS 

protruding  edges  of  poorly  made  alloy  fillings  and  abscessed  roots  of 
temporary  teeth  are  common  causes  for  these  red  and  bleeding  surfaces. 

Every  organism  has  its  vulnerable  or  vital  area  which  if  sufficiently 
injured  will  eventually  cause  its  death.  The  tooth  is  no  exception  to 
this  rule.  Its  vulnerable  point  is  the  border  of  the  peridental  mem- 
brane directly  beneath  the  gingival  margin  of  the  gum  around  the 
neck  of  the  tooth,  and  this  must  be  carefully  safeguarded.  This 
membrane  forms  the  most  vital  part  of  the  foundational  structure  of 
the  tooth.  Upon  its  health  and  resistance  depend  the  function  and 
life  of  the  whole  tooth.  If  it  becomes  injured,  irritated  or  infected  at 
its  border  and  the  lesion  or  infection  is  neglected,  the  membrane  dies 
at  this  point,  and  in  dying  it  causes  the  death  and  absorption  of  a 
similar  area  of  the  alveolar  process  which  was  in  apposition  to  the 
affected  membrane.  This  means  a  space  or  so-called  pocket  under 
the  margin  of  the  gum  where  food  debris  can  find  lodgement  and 
where  bacteria,  well  out  of  the  currents  of  the  saliva  which  flow 
freely  around  the  teeth,  can  hold  a  tenable  position. 

The  rapidity  of  the  progress  of  death  and  absorption  is  dependent 
upon  the  resistant  force  contained  within  the  cells  of  the  membrane 
and  upon  the  virulency  of  the  attacking  microorganisms.  In  child- 
hood this  membrane  is  thick  and  highly  vascular  and  can  resist  almost 
any  invasion  of  bacteria  even  when  wounded,  if  not  too  seriously. 
In  adult  life  it  gradually  becomes  thinner,  its  blood  supply  is  lessened, 
and  as  age  advances  the  cells  lose  the  high  resistant  force  that  they 
possessed  in  youth;  and  if  the  person  is  in  what  we  call  a  run-down 
condition  physically,  from  improper  feeding  of  the  body,  unclean  envi- 
ronments, harmful  habits,  excesses,  or  from  any  cause  that  will  disturb 
the  proper  metabolism  of  the  tissue  by  disturbing  the  nutritive  or  the 
nervous  systems,  the  resistant  force  is  still  further  lowered  and  the  peri- 
dental membrane  and  the  surrounding  supporting  tissues  of  the  tooth 
become  easy  prey  to  the  invading  bacterial  host.  Although  it  will 
be  possible  to  raise  the  resistance  of  this  membrane  again  by  prophy- 
lactic treatment  and  training  of  the  patient  in  the  proper  methods  of 
artificial  stimulation,  it  can  readily  be  seen  that  it  is  far  more  desirable 
to  prevent  the  original  disturbance  at  the  neck  of  the  tooth  and  save 
the  patient  the  surgical  treatment  necessary  in  the  hands  of  the  den- 
tist in  order  to  get  control  of  this  much-dreaded  and  serious  condition 
of  absorption  and  infection  of  the  supporting  tissues  of  the  root  of 
the  tooth.  It  must  always  be  borne  in  mind  that  the  most  important 
part  of  the  tooth  is  the  root  and  any  irritation  of  the  gingival  border 
of  the  gum,  especially  in  adult  life,  is  a  menace  to  that  tooth  which  is 
in  closest  proximity  to  the  point  of  irritation. 

PRACTICAL    WORK. 

In  considering  the  ])ractical  work  of  dental  prophylaxis  the  opera- 
tion in  the  mouth  of  the  adult  will  be  first  described,  for  as  a  rule  the 


PRACTICAL  WORK  303 

chiklrcM  do  not  need  iniich  instrumentation  and  their  cases  are  there- 
fore more  simple. 

In  examining  the  mouth  of  a  new  patient  regarding  the  gum  tissue 
and  the  surfaces  of  the  teeth,  the  hygienist  should  make  sure  that  the 
patient  has  removed  all  of  the  food  debris  from  the  teeth  that  it  is 
possible  to  remove  with  the  tooth-brush,  floss  silk  and  mouth  wash. 
It  is  never  the  duty  of  the  hygienist  to  operate  in  a  mouth  that 
contains  food  debris.  For  her  own  self-respect  and  for  the  dignity  of 
her  calling,  she  should  make  it  an  absolute  rule  never  to  start  an  oi)era- 
tion  of  prophylaxis  when  the  patient  has  failed  to  clean  his  teeth  of 
food  debris  before  coming  to  her  department.  It  is  never  her  duty  to 
remove  food  debris  excepting  the  small  quantities  that  roughened 
surfaces  have  made  it  impossible  for  the  patient  to  remove.  These 
cases  will  require  some  diplomacy  on  her  part,  for  she  must  realize 
that  the  patient  has  not  intentionally  insulted  her  by  presenting  such 
an  unclean  mouth.  It  is  merely  that  he  has  never  been  taught 
better.  For  years  dentists  have  consented  Avithout  remonstrance  to 
operate  in  the  mouths  from  which  the  food  has  not  been  removed  from 
between  the  teeth,  and  it  will  be  one  of  the  missions  of  the  hygienist 
toward  the  uplift  of  the  dental  profession  to  teach  the  public  that 
they  must  not  present  themselves  for  any  dental  service  whatsoever 
unless  their  teeth  have  been  thoroughly  brushed  and  flossed.  She 
should  be  kind  and  considerate  in  the  handling  of  such  cases,  and  tell 
the  patient  that  there  is  danger  of  infecting  the  gum  tissues  if  the  instru- 
ments are  used  around  the  necks  of  the  teeth  where  there  is  decompos- 
ing food,  and  that,  in  order  to  obviate  any  such  danger  it  will  be  neces- 
sary for  him  to  step  to  the  bowl  and  thoroughly  brush  and  rinse  his 
teeth  before  the  operation. 

A  stock  of  tooth-brushes  should  be  a  part  of  the  equipment  of  every 
dental  office  and  should  be  charged  up  against  the  expense  of  dental 
supplies.  The  fifteen  or  sixteen  cents  the  brushes  cost,  if  bought  in 
quantities,  amounts  to  but  little  when  we  consider  their  absolute 
necessity  for  instruction,  and  their  use  when  needed  under  these 
conditions. 

Patients  soon  learn  the  rules  of  an  office  and  in  a  comparatively 
short  time  it  will  be  a  rare  thing  to  be  obliged  to  send  a  patient  to  the 
bowl  to  brush  his  teeth  before  the  prophylactic  treatment  can  be 
started.  Much  of  the  soreness  of  the  gums  after  these  treatments  in 
the  mouths  of  new  patients  is  due  to  crowding  some  of  this  infected 
material  under  the  gum  margin  with  the  instrument,  and  it  follows 
that  the  cleaner  the  necks  of  the  teeth  are  before  instrumentation,  the 
quicker  will  be  the  recovery  of  the  congested  gums  after  treatment. 
With  a  pledget  of  cotton  soaked  with  peroxide  of  hydrogen,  the  necks 
of  the  teeth  and  also  the  approximal  surfaces  should  be  bathed.  The 
boiling  of  the  peroxide  will  mechanically  aid  in  loosening  minute  par- 
ticles of  food  debris.  After  rinsing  the  mouth  with  warm  water  the 
teeth  should  be  thoroughly  sprayed  on  all  their  surfaces  with  com- 


304  DENTAL  PROPHYLAXIS 

pressed  air  and  an  atomizer.  The  air  pressure  should  be  at  least 
twenty-five  pounds,  so  that  it  may  have  enough  force  to  blow  the  spray 
with  sufficient  speed  between  the  teeth  to  aid  in  this  mechanical 
cleansing.  It  makes  no  difference  what  liquid  is  used  in  the  atomizer 
if  it  is  harmless  and  has  a  pleasant  taste. 

Surfaces  of  the  Teeth. — ^It  must  be  remembered  that  in  this  work 
hygienists  are  not  to  cross  the  border-line  into  surgery.  The  laws  in 
all  States  prohibit  surgical  or  medicinal  treatment  by  any  but  graduate 
practitioners.  Therefore  the  entire  efforts  of  the  hygienist  are  to  be 
confined  to  the  exposed  surfaces  of  the  teeth  and  the  area  directly  under 
the  free  margin  of  the  gum. 

The  base  of  the  crown  of  each  tooth  has  four  lines  or  boundaries. 
This  is  the  entire  field  for  the  use  of  the  instruments  unless  a  root  sur- 
face is  exposed.  It  can  be  readily  appreciated  what  a  slow  and  pains- 
taking piece  of  work  it  is  to  go  over  carefully  each  of  these  surfaces 
and  remove  all  of  the  deposits  of  tartar.  In  the  first  treatments  of 
neglected  mouths  the  deposits  are  likely  to  be  large  and  are  usually 
found  on  all  the  surfaces  at  the  necks  of  the  teeth.  It  is  impossible 
to  remove  all  of  these  deposits  at  one  sitting  without  subjecting  the 
patient  to  an  unnecessary  strain.  The  large  deposits  may  be  broken 
down  and  scaled  off  and  many  of  the  smaller  nodules  can  be  removed, 
but  it  is  quite  impossible  to  be  really  thorough  in  the  first  treatment. 
Again,  it  is  unwise  to  subject  the  patient  to  a  too  strenuous  session,  for 
if  they  are  timid,  they  are  apt  to  become  discouraged  by  the  long  and 
tedious  sitting.  It  is  far  better  to  arrange  two  sittings  of  an  hour  and 
a  quarter  to  an  hour  and  a  half  each  than  one  of  two  hours  and  a  half. 
If  the  appointment  is  made  for  two  hours,  the  balance  of  the  time  may 
be  spent  in  polishing  and  in  instruction  of  the  home  care  of  the  mouth. 

The  subject  of  calcareous  deposits  has  been  so  thoroughly  covered 
by  Dr.  Kirk,  that  it  is  unnecessary  to  go  into  the  subject  very  deeply, 
but  attention  should  be  called  to  the  irritating  action  they  display  in 
their  porousness  in  absorbing  liquefied  debris,  therefore  forming  an 
excellent  retainer  for  bacteria.  It  is  absolutely  essential  for  the  health 
of  the  gums  and  the  roots  of  the  teeth  that  all  such  deposits  be  removed 
at  frequent  periods.  The  time  may  come  when  people  may  be  induced 
to  eat  the  proper  foods  in  proper  quantities,  then  this  deposit  will  be 
greatly  lessened,  but  until  this  goal  of  good  sense  is  gradually  reached, 
artificial  care  of  the  mouth  by  prophylactic  treatments  will  have  to 
be  resorted  to. 

^luch  of  the  evil  from  the  forming  of  serumal  deposits  in  the  subgin- 
gival space  can  be  obviated  by  eliminating  the  congested  condition  of 
the  capillary  circulation  found  in  the  gum  tissue  of  the  mouth  of  the 
average  adult.  But  the  mouths  are  indeed  rare  in  which  no  new 
deposits  can  be  foinid  imder  the  gingival  border  after  a  period  of  two 
months. 

System  for  Instrumentation. — In  order  to  perform  a  prophylactic 
operation  intelligently  one  must  must  work  by  system,  and  the  instru- 


PRACTICAL  WORK  305 

mentation  as  well  as  the  polishing  must  have  a  definite  starting-point 
in  the  mouth  and  should  always  proceed  in  the  same  given  direction 
over  the  surfaces  of  the  teeth  in  the  case  of  every  patient.  This  is 
necessary  for  thoroughness  and  also  in  case  of  interruption,  for  if  one 
will  but  note  mentally  the  last  tooth  being  worked  upon  before  leaving 
the  chair,  the  chain  will  remain  unbroken  upon  resuming.  It  matters 
little  what  system  is  finally  adopted,  but  the  one  here  suggested  will 
be  advocated  to  start  with. 

Lower  Jaw. — Beginning  at  the  lingual  surface  of  the  last  molar  of 
the  right  side,  lower  jaw,  at  the  gingival  line,  distolingual  angle, 
instrumentation  puoceeds  mesially  until  the  lingual  border  of  the  left 
lower  central  is  reached.    The  same  direction  is  now  followed  but  the 


8  FINISH         1  START 


Fig.  125 

line  of  operation  becomes  distal  on  the  left  side,  still  keeping  on  the 
lingual  surface  until  the  distolingual  angle  of  the  left  lower  last  molar 
is  reached. 

Again  starting  on  the  distobuccal  angle  of  the  left  lower  last  molar, 
the  instrumentation  proceeds  bucally  and  mesially  until  the  left 
lateral  is  reached,  where  from  this  point  the  operation  continues  on 
the  same  surface  to  the  distobuccal  angle  of  the  right  lower  last  molar. 

The  following  cuts  are  taken  from  Plate  VI  of  the  American  Sys- 
tem of  Dentistry,  and  will,  by  the  dotted  lines  and  arrows,  better  illus- 
trate the  directions  followed  as  just  described.  Fig.  125  represents 
the  teeth  of  the  lower  jaw  with  crowns  excised  at  the  gingival  border. 
These  cuts  will  illustrate  the  lines  to  be  followed  and  field  of  operation 
to  be  covered  by  the  dental  hygienist  with  the  instruments. 
20 


306 


DENTAl  PROPHYLAXIS 


As  shown  by  the  dotted  Hues  m  Fig.  125,  this  first  use  of  the  instru- 
ments on  the  lower  teeth  covers  only  the  lingual  and  buccal  surfaces. 
By  working  along  on  the  same  surfaces  of  the  teeth  on  the  same  jaw, 
considerable  time  may  be  saved  by  not  having  to  change  instru- 
ments every  moment  or  two,  as  one  instrument  frequently  will  adapt 
itself  to  eight  teeth  before  it  will  be  found  necessary  to  change. 


^0  0^ 


Fig.  126 


R 


After  the  deposits  have  been  removed  from  the  lingual  and  buccal 
surfaces,  attention  is  given  to  the  distal  surfaces.  Once  more  begin- 
ning on  the  distal  surface  of  the  right  lower  third  molar,  the  distal 
surface  of  the  right  lower  molars,  bicuspids  and  cuspid  are  carefully 
scraped.  Next  the  distal  surfaces  of  the  left  lower  cuspid,  bicuspids 
and  molars,  as  illustrated  in  Fig.  126.    One  instrument  will  usually 


PRACTICAL  WORK 


307 


adapt  itself  to  these  surfaces.  Next  the  mesial  surfaces  of  the  right 
lower  molars,  bicuspids  and  cuspid,  then  the  mesial  surfaces  of  the  left 
lower  cuspid,  bicuspids  and  molars.  These  surfaces,  too,  may  usually 
be  covered  with  one  instrument.  Lastly,  the  approximal  surfaces  of 
the  lower  incisors,  which  may  be  covered  with  two  instruments  (Fig. 
127). 

Upper  Jaw. — On  the  upper  jaw  at  the  point  corresponding  with  that 
where  work  was  first  started  on  the  lower  jaw,  the  distolingual  angle 
of  the  right  upper  third  molar,  the  lingual  surfaces  of  the  superior  set 
are  cleaned  of  all  calcareous  deposits,  working  mesially  until  the  left 
central  is  reached,  then  distally  to  the  left  third  molar.  Again  start- 
ing at  the  distobuccal  angle  of  the  right  upper  third  molar  the  buccal 


FINISH 


1  START 


Fig.  128 


surfaces  are  gone  over,  working  mesially  to  the  left  central  then 
distally  to  the  right  third  molar  (Fig.  128).  Now  beginning  at  the 
right  third  molar,  the  distal  surfaces  of  the  right  molars,  bicuspids  and 
cuspid  are  scraped.  Next  the  distal  surfaces  of  the  left  cuspid,  bicus- 
pids and  molars  (Fig.  129).  In  the  same  order  the  mesial  surfaces 
are  gone  over,  leaving  the  approximal  surfaces  of  lateral  and  centrals 
until  the  last  (Fig.  130). 

If  this  briefly  outlined  system  is  followed  there  will  be  but  little 
chance  that  the  deposits  may  escape  the  play  of  the  instruments. 

There  is  nothing  that  instills  a  greater  confidence  in  the  operator, 
in  the  mind  of  the  patient,  than  the  gentle  touch  of  his  hand  and  the 
instruments.    The  very  first  requisite  is  to  try  to  develop  a  firm  yet 


308 


DENTAL  PROPHYLAXIS 


gentle  touch.  In  handling  the  lips,  the  cheek,  the  tongue,  the  motions 
should  be  slow  enough  and  deliberate  enough  to  insure  gentleness. 
Such  precautions  in  self-training  soon  improve  the  technic  in  hand- 


Fig.  129 


ling  the  instruments,  and  it  is  much  the  better  fault  to  be  over- 
gentle  and  a  little  less  thorough  to  begin  with  than  to  be  heavy-handed, 
rough  and  overstrenuous  with  the  instruments.  There  is  no  better 
application  of  the  golden  rule  than  in  dentistry,  and  the  operator 


R 


5  6 


^-  4 


Fig.  1.30 


who  masters  a  fine  sense  of  touch  and  constantly  keeps  in  mind  a 
sympathetic  consideration  for  his  patient,  has  conquered  much  that 
is  productive  of  success. 


PRACTICAL  WORK 


309 


One  of  the  most  perplexing  and  yet  one  of  tlie  most  essential  things 
to  master  at  the  start  is  the  proper  handling  and  use  of  the  mouth 
mirror.  The  mouth  mirror  is  especially  essential  in  operating  on  the 
lingual  surfaces  of  the  upper  teeth  and  can  also  be  used  to  advantage 
in  holding  the  tongue  away  from  the  lingual  surfaces  of  the  lower 
teeth. 

As  the  motion  reflected  in  the  mirror  is  reversed  from  that  of  direct 
observation,  it  is  puzzling  at  first  to  place  the  instrument  properly, 
but  a  little  practice  will  soon  obWate  the  difficulty.  The  Dunn  cheek 
distender  is  used  to  expose  the  buccal  surfaces  of  the  teeth,  both  in 
instrumentation  and  polishing,  and  its  use  adds  much  to  ease  of  vision 
and  access  to  these  surfaces. 

The  Four  Motions. — In  instrumentation,  as  well  as  in  polishing,  there 
are  four  distinct  motions.     These  mav  be  termed  digital,  wrist,  rotarv 


Fig.  131 


or  forearm  and  rigid  arm.  In  acquiring  these  movements  the  fulcrum 
point  of  the  hand  in  relation  to  the  hold  of  the  instrument  is  the  deter- 
mining factor.  If  the  digital  motion  is  to  be  used,  the  instrument 
or  polisher  is  grasped  as  illustrated  in  Fig.  131.  The  end  of  the  right 
thumb  is  the  fulcrum-point  or  rest.  This  position  permits  of  a  perfect 
control  of  the  instrument  and  allows  a  play  of  the  instrument  in 
either  a  push  or  a  pull  stroke.  This  motion  is  used  particularly  on 
the  teeth  of  the  upper  jaw.  It  might  be  well  to  state  here  that  no 
instrument  should  be  used  in  the  mouth  unless  the  hand  is  first  braced 
by  a  suitable  rest  for  one  or  more  of  the  fingers  of  the  hand  holding 
the  instrument.  No  free-hand  motion  should  be  used.  Such  motions 
would  be  almost  sure  to  invite  a  slip  of  the  instrument  and  result  in 
laceration  of  the  gum  tissue.  The  wrist  motion  is  acquired  by  holding 
the  mstrument  as  illustrated  in  Fig.  132,  using  the  end  of  the  second 


310 


DENTAL   PROPHYLAXIS 


or  third  fingers  as  a  fulcrum.  This  motion  may  be  used  in  various 
parts  of  the  mouth,  especially  on  the  lingual  surfaces  of  the  molars 
and  bicuspids,  but  it  is  not  as  effective  for  general  use  as  the  forearm 
or  rotary  movements.  The  forearm  or  rotary  motion  is  used  on  both 
the  upper  and  lower  jaws  and  usually  the  end  of  the  thu'd  finger 
serves  as  fulcrum,  although  that  of  the  second  finger  can  sometimes 
be  used.  This  motion  is  produced  by  holding  the  muscles -quite  rigid, 
allowing  the  rotation  of  the  radius  around  the  ulna  bone  of  the  fore- 
arm to  play  back  and  forth  in  a  limited  area.  After  a  little  practice 
this  motion  permits  of  a  rapidity  of  work  with  the  instrument  under 
perfect  control,  and  to  master  this  stroke  is  to  master  much  of  the 
technic  of  instrumentation  and  polishing. 


Fig.  132 


rig.  1 33  illustrates  the  position  of  the  hand  when  using  the  rotary 
motion. 

The  rigid-arm  motion  is  used  for  polishing  nearly  all  of  the  labial 
and  buccal  surfaces  of  the  teeth,  both  upper  and  lower,  and  for  the 
lingual  surfaces  of  the  molars  and  bicuspids.  The  rest  is  usually  found 
by  using  the  side  of  the  second  joint  of  the  right  thumb  on  the  chin  or 
the  second  joint  of  the  third  or  fourth  finger  as  illustrated  in  Fig.  134. 

The  muscles  of  the  whole  arm  are  made  fairly  tense  and  the  arm  is 
made  to  travel  forward  and  backward  in  a  short,  limited  area.  All 
of  these  motions  should  be  practised  over  and  over  again  on  manikins 
or  on  natural  teeth  set  in  modeling  compound  before  being  tried  in  the 
mouth.  They  are  not  easy  to  master  and  the  nuisdes  must  be  trained 
by  repeated  practise. 


PRACTICAL  WORK 


311 


In  the  removal  of  tartar  around  the  necks  of  the  teeth,  there  are 
two  strokes  that  may  be  utilized,  a  push  stroke  and  a  pull  stroke. 
Which  to  use  is  determined  in  a  great  measure  upon  the  quantity  or 
bulk  of  the  deposit  and  also  upon  the  tenacity  with  whicli  it  may  cUng 


Fig.  133 


to  the  tooth  surface.  In  scaling  off  pieces  of  hard  deposits,  large  or 
small,  the  draw'  or  pull  stroke  will  be  found  most  effective.  The  instru- 
ment is  carefully  carried  a  little  below  the  gingival  border  of  the  gum 
and  hooked  securely  over  the  shoulder  of  the  deposit.    Then  with  the 


Fig.  134 


hand  properly  braced,  the  instrument  is  firmly  drawn  toward  the  masti- 
cating surface  or  cutting  edge  of  the  tooth — a  second  digital  motion. 
When  the  deposits  are  small  and  fairly  soft,  a  short,  pushing  stroke 
will  be  more  effective. 


312 


DENTAL  PROPHYLAXIS 


INSTRUMENTATION 


313 


Instruments. — Before  the  handling  of  the  instruments  is  described 
in  detail  a  set  of  scalers  will  be  considered  that  should  be  sufficient 
for  the  beginner  for  all  {Jrophylactic  work  upon  the  necks  and  crowns 
of  the  teeth.  These  include  nine  instruments  and  may  be  described 
as  follows: 

P'ig.  135.  The  two  small  curved  instruments  with  the  spoon-like 
ends  are  known  as  Nos.  17  and  18  of  the  set  of  Darby-Perry  excava- 
tors. They  are  curved  in  opposite  directions  to  each  other  and  are 
paired  as  rights  and  lefts.  Dr.  C.  W.  Strang,  of  Bridgeport,  Ct., 
suggested  their  use.  Nos.  6  and  7  belong  to  the  D.  D.  Smith  set  and 
are  made  by  J.  W.  Ivory,  of  Philadelphia.  Fig.  136,  Nos.  13  and  14 
were  designed  by  Dr.  E.  S.  Gaylord,  of  New  Haven,  Ct.,  and  are  a 


Fig.  137 


part  of  the  Smith  set.  They  are  also  made  by  J.  W.  Ivory.  No.  3 
sickle-shaped  instrument  is  made  by  the  S.  S.  White  Company,  and 
is  used  for  the  removal  of  heavy  deposits  by  the  pull  or  digital  stroke. 
Fig.  137  illustrates  Nos.  3  and  4  from  the  Harlan  set  of  scalers  made 
by  the  S.  vS.  White  Company. 


INSTRUMENTATION. 

Lower  Jaw. — Assuming  that  the  deposits  are  not  unusual  in  quantity 
and  are  reasonably  easy  to  remove,  the  adaptation  of  these  instru- 
ments will  be  described,  proceeding  as  in  Fig.  125. 

Starting  at  the  distolingual  angle  of  the  last  lower  right  molar, 
No.  18  of  the  Darby-Perry  excavators  is  selected  and  held  at  an  angle, 


314 


DENTAL  PROPHYLAXIS 


as  sho\Aai  in  Fig.  138.  The  stroke  used  is  a  short  downward  push,  and 
a  ^^Tist  motion  is  used  with  the  blade  held  at  nearly  a  right  angle  with 
the  tooth.  On  the  downward  stroke,  the  back  of  the  blade  with  its 
smooth,  blunt  surface  will  strike  the  gingival  border  of  the  gum  and 
prevent  the  cutting  edge  of  the  instrument  from  traveling  far  enough 
to  injure  the  peridental  ligament.  This  short  stroke  is  rapidly  repeated, 
the  operator  making  a  wave-like  motion  of  the  instrument,  gradually 
moving  it  forward,  mesially,  on  the  lingual  surface  of  the  molar  until 
the  mesiolingual  angle  is  tiu-ned,  and  using  the  mouth  mirror  with 
the  left  hand  to  keep  the  tongue  out  of  the  way.  The  instrument  is 
now  transferred  to  the  next  molar  and  the  operation  is  repeated.    This 


Fig.  138 

is  continued  with  the  same  instrument  until  the  left  lower  central  is 
reached,  from  No.  1  to  No.  2  in  Fig.  125.  The  mate  to  this  instrument, 
No.  17,  is  now  substituted  and  the  operator,  starting  on  the  lingual 
surface  of  the  left  central.  Fig.  i:3(),  and  using  a  rotary  stroke,  continues 
until  the  distolingual  angle  of  the  left  lower  last  molar  is  reached, 
Fig.  140  or  from  No.  3  to  No.  4  in  Fig.  125.  These  small  instruments 
greatly  magnify  the  sense  of  touch,  so  that  each  small  deposit  is  readily 
felt,  whereas  a  larger  instrument  might  pass  it  })y. 

Again  starting  at  the  distolniccal  angle  of  the  left  last  molar  with 
instrument  No.  18,  Fig.  141,  this  short,  pushing  stroke  with  a 
wrist  motion  is  used  until  the  left  lateral  is  reached.  From  No.  5  to 
No.  G  in  Fig.  125.    Altliough  the  same  instrument  can  be  used  eft'ec- 


INSTRUMENTATION 


315 


lively  on  the  lal)ial  surfaces  of  the  incisors,  it  will  be  found  advanta- 
geous to  change  for  its  mate,  No.  17,  and,  leaning  slightly  in  front  of  the 


Fig.  139 


Fig.  140 


patient,  brace  the  hand  by  the  thu-d  finger  on  the  masticating  surface 
of  the  first  bicuspid  (Fig.  142),  using  a  wrist  motion  which  permits 


316 


DENTAL  PROPHYLAXIS 


Fig.  141 


Fig.  142 


INSTRUMENTATION 


317 


of  a  careful  handling  of  the  festoons  of  the  lower  incisors.  After 
the  labial  surface  of  the  left  lateral  is  finished,  the  hand  is  moved 
forward  to  engage  the  next  tooth.  At  the  right  cuspid  the  rotary  stroke 
is  now  adopted  and  continued  to  the  last  molar.  Fig.  143  or  from  No. 
7  to  No.  8  in  Fig.  125.  The  finger  rests  for  the  work  just  described  are 
found  on  the  masticating  surfaces  of  the  bicuspids  or  on  the  cutting 
edge  of  the  cuspids  or  incisors. 

The  base  of  each  tooth  has  four  lines.  Two  of  these  lines  have  now 
been  covered,  and  there  remains  the  approximal  surfaces  or  the  distal 
and  mesial  lines.     No.  13  is  an  instrument  with  the  end  bent  at  an 


Fig.  143 


angle  of  forty-five  degrees,  having  a  long  blade  with  a  file-cut  surface, 
the  numerous  small  blades  of  which  are  very  effective  in  removing 
the  small  deposits.  This  instrument  should  be  used  chiefly  with 
a  pull  stroke,  starting  at  No.  1,  in  Fig.  126,  which  is  the  distal  sur- 
face of  the  right  lower  last  molar,  as  shown  in  Fig.  144.  The  distal 
surface  of  the  last  molar  being  free,  the  blade  is  carefully  passed 
down  under  the  gum  line  until  the  sense  of  touch  determines  the  bot- 
tom of  the  subgingival  space.  The  blade  is  then  brought  tight  against 
the  tooth  surface  and  pulled  upward.  An  eighth  to  a  quarter  of  an 
inch  play  of  the  blade  is  sufficient  to  dislodge  the  deposits.    This  stroke 


318 


DENTAL  PROPHYLAXIS 


is  rapidly  repeated  across  the  back  of  the  tooth.     In  adapting  this 
instrument  to  the  distal  surface  of  the  second  molar  the  blade  is  inserted 


Fig.  144 


Fifj.  145 


sidewise  from  the  buccal  surface  (Fig.  145),  and  with  a  short  push-and- 
pull  stroke  the  instrument  is  worked  between  the  teeth   in  order  to 


INSTRUMENTATION 


319 


cover  the  entire  distal  line.  If  the  teeth  are  so  shaped  and  are  so 
close  together  that  they  will  not  permit  the  blade  to  pass  between  them, 
then  the  instrument  should  be  inserted  also  from  the  lingual  surface 


Fig.  146 


and  in  this  way  that  part  of  the  distal  line  that  was  inaccessible  from 
the  buccal  surface  is  covered.  With  the  same  instrument  the  distal  sur- 
faces of  the  teeth  may  be  scaled  to  the  incisors,  or  from  No.  1  to  No.  2, 
in  Fig.  126.    Again,  with  the  same  instrument,  the  operator  should  start 


Fig.  147 


on  the  distal  surface  of  the  left  cuspid,  and  entering  from  the  buccal  side, 
proceed  on  to  the  last  molar,  or  from  No,  3  to  No.  4,  in  Fig.  126.  The 
procedure  for  the  mesial  surfaces  is  the  same  as  described  for  the  distal, 


320 


DENTAL  PROPHYLAXIS 


except  that  the  instrument  used  is  Xo.  14,  and  one  position  is  ilhistrated 
as  in  Fig.  146.  Both  push  and  pull  strokes  are  employed.  The  lower 
incisors  are  scaled  on  their  approximal  surfaces  by  the  bayonet-shaped 
Smith  scalers,  Nos.  6  and  7,  from  No.  5  to  No.  6  of  Fig.  127,  which 
shows  this  area.  Fig.  147  illustrates  the  adaptation  of  these  instruments. 
Upper  Jaw. — On  the  upper  jaw,  at  the  right  distolingual  angle  of  the 
last  molar,  instrument  No.  17  is  placed  at  nearly  a  right  angle  with  the 
tooth  and,  with  the  hand  braced  on  the  top  of  the  left  lower  lateral 
and  cuspid  teeth,  using  the  third  finger  as  fulcrum  (Fig.  148),  a  wrist 
and  digital  motion  is  employed,  the  instrument  being  made  to  travel 
forward  with  a  short  up-and-down,  push-and-pull  stroke  combined, 
perhaps  better  described  as  a  waving  stroke.  The  fulcrum-point  is 
maintained,  the  instrument  being  drawn  in  or  shortened  as  the  inci- 
sors are  approached.     When  the  left  central  is  reached  (Fig.  128), 


Fig.  148 


instrument  No.  18  is  substituted,  the  second  finger  used  as  a  fulcrum 
on  the  cutting  edge  of  the  right  upper  cuspid  (Fig.  149),  and  the  lingual 
surfaces  of  the  upper  teeth  of  the  left  side  are  gone  over  with  a  wrist 
and  digital  motion.  This  fulcrum-point  is  maintained  and  the  instru- 
ment advanced  in  length  with  the  tiuunb  and  first  finger  (Fig.  150). 
Again  starting  at  the  distobuccal  angle  of  the  left  upper  third  molar, 
the  third  finger  is  placed  slightly  back  of  the  cutting  edge  of  the  right 
upper  lateral  and  central  while  the  second  finger  rests  on  the  cutting 
edge  of  the  left  upper  central  (Fig.  151).  This  i)osition  can  be  held  until 
the  left  lateral  is  reached,  the  motion  })eing  wrist  and  digital.  Shifting 
the  fulcrum-point  to  the  end  of  the  third  finger  on  the  edge  of  the  right 
upper  cuspid,  the  labial  surfaces  of  the  left  central  and  lateral  may  be 
scaled  with  the  same  instrument.  With  the  hand  resting  against  the 
chin  just  below  the  lower  lip,  and  the  third  joint  of  the  little  finger 
serving  as  a  fulcrum,  with  instrument  No.  18,  the  right  central  and 


INSTRUMENTATION 


321 


from  there  back  to  and  inctuding  the  third  molar  is  scaled,  using  the 
digital  motion,  as  in  Fig.  152. 

The  lingual  as  well  as  the  labial  and  buccal  surfaces,  having  been 
covered,  No.  13  is  used  for  the  distal  surfaces  (Fig.  129)  of  all  the  upper 
teeth  excepting  the  incisors.  For  the  molars,  bicuspids  and  cuspids  of 
the  upper  jaw  the  description  of  the  use  of  this  instrument  for  those 
on  the  lower  jaw  may  be  applied,  the  hand  rest  being  found  chiefly 
on  the  cutting  edge  of  the  lower  incisors,  the  end  of  the  third  finger 


Fig.  149 


serving  for  fulcrum.  No.  14,  P"ig.  153,  is  used  in  a  similar  manner  with 
the  hand  rests  the  same  as  for  No.  13.  Nos.  5.  and  G  are  best  adapted 
for  the  approximal  surfaces  of  the  incisors,  their  use  at  this  point  being 
too  self-evident  to  need  explanation. 

Even  with  this  detailed  description,  much  will  be  found  lacking  to 
the  beginner,  but  after  a  little  prastice  on  the  manikin  the  hand  will 
soon  adjust  itself  to  the  proper  rests  to  secure  the  greatest  efficiency 
and  control  of  the  instrument. 
21 


322 


DENTAL  PROPHYLAXIS 


In  removing  the  heavy  deposits  the  sickle-shaped  instrument,  No. 
3,  will  be  found  most  useful.     In  skilful  hands  it  is  possible  to  scale 


Fig.  150 


Fig.  151 


INSTRUMENTATION 


323 


roughly  nearly  all  the  surfaces  of  all  the  teeth  with  this  one  instrument, 
the  exception  heinji;  approximal  surfaces.     It  is  used  with  a  draw  or 


Fig.  152 


Fig.  153 


pull  stroke  and  has  the  advantage  of  not  being  dangerous  around  the 
anterior  teeth,  for  the  point  of  the  instrument  as  well  as  the  side  of 


324  DENTAL  PROPHYLAXIS 

the  blade  is  inserted  under  the  deposit  and  pulled  directly  upward  on 
the  lower  teeth  and  downward  on  the  upper  teeth.  But  in  the  back  of 
the  mouth  where  its  adaptation  necessitates  the  drawing  of  the  instru- 
ment forward  under  the  border  of  the  gingiva,  the  point  is  likely  to 
slip  and  travel  too  deep  into  the  subgingival  space  unless  care  is  used. 
A  firm  hold  on  the  instrument  and  a  secure  brace  of  the  hand  is  abso- 
lutely essential.  This  sickle-shaped  instrument  is  used  almost  entirely 
with  a  digital  motion  and  the  two  principal  positions  are  illustrated 
in  Figs.  154  and  155.  It  is  very  difficult  to  scale  the  teeth  thoroughly 
with  this  instrument,  but  the  larger  deposits  having  been  removed 
at  the  first  sitting,  Nos.  17  and  18  can  be  used  to  advantage  at  the 
second  and  all  subsequent  treatments. 

The  Harlan  instruments,  Nos.  3  and  4,  are  also  used  with  a  draw 
stroke  and  are  helpful  in  removing  the  small,  hard,  tenacious  deposits 
under  the  free  margin  of  the  gums.  They  are  adaptable  in  nearly  all 
sections  of  the  mouth  and  their  use  is  usually  self-suggestive.  When 
these  small  deposits  resist  Nos.  17  and  18,  especially  on  the  bicuspids, 
cuspids  and  incisors,  these  Harlan  instruments  will  be  found  very 
effective. 

If  uncertainty  exists  in  the  mind  regarding  the  thorough  removal 
of  all  deposits,  an  instrument  known  as  an  explorer  carefully  passed 
around  the  neck  of  the  tooth  under  the  gingivae  will  readily  detect 
any  small  deposits  or  uneven  surfaces.  The  smaller  the  instrument, 
the  more  greatly  is  the  sense  of  touch  magnified.  It  is  for  this  reason 
that  the  use  of  Nos.  17  and  18  is  advised  wherever  practical. 

There  are  two  special  features  to  be  considered  under  instrumenta- 
tion. First,  the  sensitiveness  that  is  frequently  found  around  the  necks 
of  the  teeth,  and  second,  the  bleeding  of  the  gingival  borders  of  the 
gums.  In  adults  where  the  lime  deposits  have  been  heavy,  their  removal 
will  frequently  cause  much  sensitiveness  for  a  week  or  two,  sometimes 
even  longer,  to  heat  and  cold  and  to  sweets  and  acids.  The  deposits 
have  caused  an  absorption  of  the  border  of  the  alveolar  process  and 
the  soft  tissues  around  the  necks  of  the  teeth,  and  when  they  are 
removed  a  portion  of  the  cementum  is  exposed  which  later  disappears 
and  exposes  the  interglobular  spaces  on  the  border  between  the  dentin 
and  the  cementum,  forming  an  area  that  is  highly  sensitive  to  the 
touch  of  the  instrument  or  polisher.  It  is  frequently  wise  to  inform 
the  patient  that  he  may  expect  the  surfaces  to  be  responsive  to  heat 
and  cold  for  a  short  time,  in  order  to  allay  any  fears  on  his  part.  The 
deposits  acting  as  a  covering  for  these  surfaces  have  protected  them 
from  extern'al  irritation,  and  the  patients  are  apt  to  wonder  why  it  is 
that  their  mouths  are  so  much  more  sensitive  than  they  were  before 
the  deposits  were  removed.  Acids  are  especially  irritating  to  these 
surfaces  and  the  use  of  bicarbonate  of  soda,  half  a  teaspoonful  to  a 
third  of  a  glass  of  warm  water,  used  as  a  mouth  wash  two  or  three 
times  daily,  will  aid  greatly  in  tiding  over  this  short  period  of  discom- 
fort.    If  the  soda  can  be  used  clear  by  dipping  the  finger  in  water, 


INSTR  U  ME  NT  A  TION 


325 


Fig.  154 


Fig.  155 


326  DENTAL  PROPHYLAXIS 

touching  it  to  the  soda  and  then  rubbing  it  on  these  surfaces,  it  will 
all  the  more  quickly  neutralize  any  acid  that  may  be  irritating 
to  this  sensitive  tissue.  The  thorough  rubbing  and  polishing  with 
the  stick  and  pumice  and  the  extreme  cleanliness  from  the  faithful 
use  of  the  tooth-brush  will  soon  bring  these  troublesome  areas  under 
control.  A  10  per  cent,  solution  of  nitrate  of  silver  is  sometimes 
advised,  but  if  it  is  used,  it  should  be  followed  by  a  thorough  polishing 
with  the  stick  and  pumice. 

The  second  feature,  which  will  be  considered  briefly,  is  the  bleed- 
ing of  the  gums  during  instrumentation.  When  the  gums  readily 
bleed  there  is  congestion  of  the  capillaries,  and  the  more  blood  allowed 
to  escape  from  the  gingivae,  the  sooner  the  congestion  will  be  relieved. 
Instead  of  trying  not  to  make  the  gums  bleed,  just  the  reverse  course 
should  be  followed,  although  of  course  this  does  not  mean  that  they 
should  be  lacerated  or  the  tissue  wounded.  The  bleeding  process  is 
produced  by  using  the  back  or  smooth  surface  of  the  blade  of  the  instru- 
ment with  pressure,  and  this  is  done  while  removing  the  lime  deposits, 
and  if  there  is  a  copious  flow  of  blood  from  some  of  the  approximal 
surfaces,  it  should  be  encouraged  by  rapid,  gentle  pressure  strokes 
directly  on  the  gingivae.  Healthy  gums  will  not  bleed  during  instru- 
mentation, and  when  bleeding  occurs  enlarged  and  congested  capilla- 
ries are  sure  to  be  found.  No  fear  of  causing  injury  to  the  gum  tissue 
in  causing  a  flow  of  blood  need  be  felt  as  long  as  care  is  taken  that 
the  blade  of  the  instrument  does  not  cut  the  tissue.  Frequently  after 
such  a  treatment  the  gums  will  take  on  a  color  two  shades  lighter  before 
the  patient  leaves  the  chair,  and  after  a  few  days  of  stimulation  with 
the  tooth-brush  it  will  be  hard  to  recognize  it  as  the  deep  red,  congested 
tis.sue  that  it  was  at  first. 

POLISHING.  • 

It  is  impossible  to  obtain  the  same  results  in  prophylaxis  with  the 
use  of  the  dental  engine  in  polishing  as  may  be  secured  with  the  hand 
polishers.  This  belief  is  based  upon  personal  experience  in  faithfully 
trying  out  both  methods,  and  is  an  accepted  fact  by  all  prophylactic 
workers  who  have  become  proficient  with  the  hand  polishers. 

The  object  of  this  polishing  process  is  threefold.  First,  the  removal 
of  stains,  placques  and  films  or  all  soft  accretions  on  the  exposed  sur- 
faces of  the  teeth.  Second,  a  polishing  of  the  enamel  surfaces  and  a 
stimuhiting  ett'ect  that  seems  to  be  imparted  to  the  living  tissue  of 
the  tooth  itself  by  the  vigorous  massage.  Third,  the  beneficial  results 
obtained  on  the  gingival  borders  of  the  gums  by  the  slight  bumping 
of  the  stick,  causing  light  i)ressure  and  release  which  imparts  a  massage 
effect  and  aids  greatly  in  producing  a  perfect  flow  of  blood  through 
the  capillaries  in  the  peripheral  circulation.  If  a  new  case  presents 
itself  in  which  the  teeth  are  very  badly  stained,  it  is  perfectly  reason- 
able, if  desired,  to  use  the  dental  engine  for  the  first  treatment  to  aid 


POLISHING 


327 


in  cleaning  off  these  stains  from  the  enamel  surfaces,  but  all  subsequent 
treatments  should  be  made  with  the  hand  polishers.  An  engine 
revolving  at  six  or  eight  hundred  revolutions  a  minute,  with  the  rubber 
cup  or  buff  charged  with  pumice,  cuts  too  viciously  and  if  used  at  each 
prophylactic  treatment,  will  in  time  affect  the  enamel  and  tooth  struc- 
ture at  the  necks  of  the  teeth.  With  the  dental  engine  all  sense  of  touch 
is  lost,  and  besides  it  is  not  as  adaptable  on  the  approximal  surfaces 
or  on  the  surfaces  of  the  molars  as  the  stick  held  in  the  hand.  The 
gingival  borders  of  the  gums,  in  many  mouths,  have  been  badly 
wounded  or  damaged  by  the  revolving  cups  or  buffs  in  the  dental 
engine,  and  if  one  hopes  and  expects  to  secure  the  best  results  in  obtain- 
ing ideal  health  conditions  of  these  tissues,  one  must  become  proficient 


i 

w 

1 

Fig.  156 


with  the  hand  polishers.  Those  who  would  advocate  the  dental  engine 
are  those  who  have  failed  to  make  themselves  proficient  with  the  hand 
polishers.  There  can  be  no  choice  if  the  latter  is  faithfully  tried.  There 
are  a  number  of  different  woods  that  may  be  used  for  polishing,  as 
cedar,  maple,  hard  pine,  etc.,  but  the  closest-grained  wood  and  the  one 
best  adapted  for  this  purpose  is  orange  wood.  There  are  two  sizes  of 
sticks  that  may  be  had  from  the  dental  depots,  known  as  large  and  small. 
The  large  size  is  cut  about  three  quarters  of  an  inch  in  length  and  one 
end  is  cut  wedge-shaped.  This  stick  is  used  on  all  the  broad  surfaces 
of  the  teeth  excepting  the  masticating  surfaces.  The  small  stick  is 
cut  about  the  same  length  and  one  end  is  cut  like  the  point  of  a  lead- 
pencil.  The  smaller  stick  is  used  on  the  approximal  surfaces  and  around 
the  necks  of  the  teeth  where  it  is  impossible  to  adapt  the  larger  stick. 


328 


DENTAL  PROPHYLAXIS 


In  order  to  work  with  facility,  two  holders  for  the  two  sizes  of  sticks 
should  be  employed.  Fig.  156  illustrates  the  Jack  porte  polishers  with 
sticks  in  position. 

As  a  slight  abrasive  and  polish  to  be  used  with  the  sticks,  the  finest 
grade  of  pumice  moistened  with  water  will  prove  to  be  the  most  satisfac- 
tory. Although  other  polishing  mediums  are  used  with  good  results,  it 
is  doubtful  if  there  is  anything  superior  to  fine  pumice  for  this  special 
work.  A  scant  spoonful  placed  in  a  small  porcelain  dish,  and  wet 
sufficiently  with  water  to  be  almost  liquid,  will  make  a  mixture  that 
can  readily  be  picked  up  on  the  point  of  the  wet  stick  and  used  in  the 
mouth. 

System  for  Polishing. — Just  as  a  definite  system  is  employed  in  going 
over  the  teeth  with  the  instruments,  so  should  a  system  for  reaching 
all  surfaces  of  the  teeth  with  the  polishers  be  followed. 


Fig.  157 


The  following  system  is  very  effective  and  its  adoption  is  suggested, 
at  least  for  beginners: 

Starting  on  the  labial  surface  of  the  right  upper  central  with  the 
large  stick,  the  polishing  progresses  backward  to  the  right  lateral, 
then  to  the  right  cuspid  and  so  on  until  the  right  last  molar  is  reached. 
I'rom  this  point  start  on  the  buccal  surface  of  the  right  lower  last  molar 
and  progress  forward  around  the  buccal  and  labial  surfaces  of  all  the 
lower  teeth  to  the  left  lower  last  molar.  Transferring  the  stick  to  the 
buccal  surface  of  the  left  upper  last  molar,  the  polishing  is  continued 
forward  to  the  median  line  to  and  including  the  left  upper  central. 
All  the  labial  and  buccal  surfaces  have  now  been  polished  with  the  use  of 
only  the  larger  stick.  Fig.  1 57  illustrates  direction  for  polishing.  Then 
starting  on  the  lingual  surface  of  the  right  lower  last  molar  with  the 
large  stick,  the  polishing  of  the  lingual  surfaces  proceeds  forward  to 
the  incisors,  then    backward,  or   distally,  to   the   lingual  surface  of 


POLISHING 


329 


the  left  lower  last  molar.  Again  beginning  on  the  lingual  surface  of 
the  left  upper  last  molar,  all  of  the  lingual  surfaces  are  covered,  ending 
on  the  right  upper  last  molar. 

So  far  only  the  large  stick  has  been  used.  Now  with  the  pointed 
stick  the  same  course  should  be  followed  over  the  teeth  as  has  just 
been  described,  polishing  in  between  the  teeth  as  far  as  possible  and 
rubbing  the  necks  of  the  teeth  under  the  free  border  of  the  gingiva?, 
keeping  the  edges  of  the  sticks  sharp.  When  they  become  frayed  or 
brush-like,  they  should  be  trimmed  off  with  a  pair  of  scissors,  or  if, 
after  this,  the  edges  are  still  too  blunt,  sharpened  with  a  knife. 

The  polishing  is  confined  almost  entirely  to  two  motions,  the  rigid- 
arm  and  the  forearm  or  rotary.  The  one  exception  is  the  digital  that 
should  be  used  by  beginners  on  the  labial  surfaces  of  the  upper  incisors. 


Fig.  158 


In  order  to  polish  effectively  pressure  must  be  used.  It  is  this  one 
point  of  being  able  to  apply  pressure  on  all  the  surfaces  while  polish- 
ing that  makes  the  operation  difficult.  This  is  noted  especially  in 
polishing  the  lingual  surfaces  of  the  molars  and  bicuspids.  The  proper 
hand  rests  are  essential  and  also  muscular  practise  of  the  motions 
used  for  this  work. 

Beginning  on  the  labial  surface  of  the  right  upper  central  with  the 
large  stick,  and  using  a  digital  motion,  the  stick  is  made  to  travel  up 
and  down  the  full  length  of  the  face  of  the  tooth,  rubbing  the  surface 
with  both  up  and  down  strokes.  The  stick  is  allowed  to  bump  the 
gum  lightly  but  not  hard  enough  to  cause  discomfort.  Considerable 
pressure  is  used  and  the  motion  is  rapid.  Fig.  158  illustrates  the  posi- 
tion of  the  hand  with  the  thumb  rest  on  the  cuspid  for  the  digital 
motion.    When  the  right  cuspid  is  reached  the  rigid-arm  motion  is 


330 


DENTAL  PROPHYLAXIS 


employed,  with  the  back  of  the  second  finger,  between  the  second  and 
third  joints,  resting  on  the  chin  and  the  two  bicuspids  are  rubbed  and 


Fig.  159 


Fig.  160 


polished  up  and  down  or  longitudinally,  the  right  thumb  pressing  on 
the  polisher  at  the  end  of  the  stick  (Fig.  159).  Now  inserting  the 
Dunn  cheek  distender,  the  buccal  surfaces  of  the  molars  are  rubbed 


POLISHING 


331 


crosswise,  using  the  rotary  motion  and  the  same  fulcrum  position 
that  was  used  with  the  cuspid  and  bicuspid,  but  the  porte  polisher 
is  shifted  in  the  hand  and  grasped  as  one  woidd  hold  a  pen-holder 
(Fig.  160).  The  end  of  the  stick  may  be  made  to  travel  up  and 
down  part  way  on  the  approximal  surfaces,  but  the  principal  motion 
for  polishing  is  crosswise.  The  polishing  of  the  right  lower  molars 
is  the  same  as  described  for  the  upper  molars.  For  the  right  lower 
cuspids  and  bicuspids,  the  same  as  for  the  upper.  The  first  finger 
of  the  left  hand  now  is  placed  across  the  inside  of  the  lip  to  depress 
it  and  with  the  polisher  grasped  in  the  fist  with  right  thumb  resting 
on  the  left  forefinger  (Fig.  161),  the  lower  incisors  are  polished.  For 
the  left  cuspid  and  bicuspids  the  same  position  as  for  the  right  is  used. 
In  polishing  the  left  lower  and  upper  molars  the  back  of  the  third  finger 


Fig.  161 


becomes  the  fulcrum  on  the  side  of  the  chin  and  the  polisher  is  grasped 
pen-holder  fashion,  as  in  Fig.  162,  using  the  rigid-arm  motion.  The 
descriptions  of  the  right  cuspid  and  bicuspids,  lateral  and  central,  will 
apply  to  the  left.  It  will  be  noted  that,  with  the  exception  of  the 
upper  incisors  and  right  molars,  the  motion  used  on  all  the  outer  sur- 
faces of  the  teeth  has  been  rigid-arm.  That  on  the  inner  surfaces  of 
both  lower  and  upper  is  forearm  or  rotary.  The  difficulty  met  with  is 
that  of  producing  pressure  and  at  the  same  time  retainmg  control  and 
length  of  stroke.  With  the  mouth  mirror  in  the  left  hand  to  hold  the 
tongue  away,  the  back  of  the  third  and  fourth  fingers  are  pressed  against 
the  chin,  and  the  polisher  held  as  the  pen-holder  in  a  rigid  grasp  (Fig. 
163),  the  stick  is  made  to  travel  up  and  down  on  the  inner  surface  of 


332 


DENTAL  PROPHYLAXIS 


Fig.  162 


Fig    103 


POLISHING 


333 


the  right  lower  molars,  the  edge  of  the  stick  pointing  up  and  down  with 
the  long  axis  of  the  tooth.  This  polishing  motion,  it  will  be  noted, 
is  just  the  reverse  from  that  used  on  the  buccal  surfaces.    By  shorten- 


FiG.  164 


Fig.  165 


334 


DENTAL  PROPHYLAXIS 


ing  the  hold  on  the  poHsher  the  same  position  is  used  for  polishing 
the  bicuspids  and  cuspids. 

Other  adaptations  of  the  stick  will  be  found  that  are  advantageous 


Fig,  166 


Fkj.  1 07 


POLISHING 


335 


for  these  surfaces,  such  as  using  the  side  of  the  stick  with  an  up-and- 
down  stroke  instead  of  its  sharpened  end. 

By  leaning  forward  in  front  of  the  patient  the  second  finger  is  placed 
on  the  top  of  the  left  cusi)id  or  bicuspid  and  with  a  rocking  or  rotary 


Fig.  168 


Fig.  169 


motion  of  the  arm  and  stick  the  lower  incisors  are  polished  (Fig.  164). 
The  left  lower  molars  are  polished  with  the  same  pen-holder  grasp,  using 
the  second  finger  as  a  fulcrum  on  the  right  lower. cuspid  or  lateral 


336 


DENTAL  PROPHYLAXIS 


(Fig.  165).  The  mouth  mirror  can  be  used  to  good  advantage  while 
polishing  the  lingual  surfaces  by  having  the  patient  sit  low  enough  in  the 
chair.  Starting  on  the  lingual  siu-face  of  the  left  upper  last  molar,  the 
porte  polisher  is  held  like  the  pen-holder  and,  with  the  end  of  the  third 
finger  resting  on  the  labial  surface  of  the  right  lower  cuspid  (Fig.  166), 
the  molars  are  rubbed  chiefly  up  and  down  with  the  edge  of  the  stick. 
Holding  the  same  fulcrum-point,  the  grasp  on  the  polisher  is  gradually 
shortened  and  the  incisors  are  polished  as  shown  in  Fig.  167.  The 
lingual  surfaces  of  the  left  cuspid,  bicuspids  and  molars  are  polished 
with  the  same  hold  of  the  polisher,  the  rest  being  found  on  the  chin, 
using  the  back  of  the  second  joint  of  the  third  finger  (Fig.  168).  The 
motion  used  is  mostly  forearm  or  rotary. 


Fig.  170 


All  of  the  positions  and  fulcrum-points  described  for  the  large  stick 
apply  also  to  the  small  stick.  The  pointed  stick  is  used  between 
the  teeth,  rubbing  the  surfaces  as  far  as  the  stick  can  reach  and 
also  around  the  necks  of  the  teeth  on  all  of  the  surfaces.  Its  use 
should  start  at  the  same  point,  the  right  upper  central,  and  travel 
over  the  teeth  with  the  same  system  as  that  described  for  the  large 
stick.  The  points  of  both  polishers  should  be  kept  trimmed  with  the 
scissors  and  when  they  become  too  blunt,  sharpened  with  a  knife. 
Where  the  gums  between  the  teeth  are  congested,  the  side  of  the  stick 
is  pressed  against  them  with  a  fast,  quick  stroke  to  encourage  the 
bleeding.  Care  should  be  taken  in  the  use  of  both  sticks  not  to  abrade 
the  gingivte,  but  the  light  pressure  with  the  side  of  the  stick  against 
the  gum  margin  will  prove  very  beneficial  (Fig.  169).  AVhen  sensitive 
surfaces  are  found  at  the  necks  of  the  teeth,  the  pointed  stick  freely 


POLISHING 


337 


charged  with  pumice  is  appUed  with  vigor  and  considerable  pressure. 
A  thorough  poUshing  of  their  surfaces  will  greatly  aid  in  reducing  the 
sensitiveness. 

Floss  Polishing. — After  polishing  with  the  sticks  there  still  remain 
the  contact  points  and  an  area  on  the  approximal  surfaces  that  have 
not  been  reached.  By  doubling  a  length  of  ligating  silk,  twisting  it 
and  dipping  it  in  water  and  then  in  pumice,  these  surfaces  may  be 
polished  quite  effectually.  When  the  teeth  are  very  close  together  a 
single  strand  will  be  found  sufficient,  as  this  silk  is  larger  in  size  than 
that  sold  for  every-day  flossing.  Cutters'  wide  floss  may  also  be  used 
to  advantage  where  the  space  will  permit.  When  using  the  floss  for 
polishing  it  should  be  passed  between  the  contact  points  with  care, 


Fig.  171 


so  that  it  will  not  snap  on  the  gum,  drawn  back  and  forth  on  the  distal 
surface  of  the  tooth  and  then  pressed  backward  rubbing  the  mesial 
surface  of  the  adjoining  tooth.  Most  of  the  decay  takes  place  in  these 
surfaces  and  they  must  be  given  careful  attention.  If  the  ends  of  the 
floss  are  wound  around  the  first  fingers  as  illustrated  in  Figs.  170  and 
171,  it  can  be  easily  manipulated. 

Brush  Wheel. — The  masticating  surfaces  are  so  uneven  that  a  stick 
cannot  be  used  on  them  very  well,  so  it  will  be  necessary  to  use  a  brush 
wheel  in  the  engine  to  reach  down  in  the  fissures  to  polish  these  surfaces. 
With  the  wheel  dipped  in  water  and  the  edge  of  it  touched  to  wet 
pumice,  the  engine  should  be  run  at  a  moderate  speed  and  the  edge 
22 


338  ■  DENTAL  PROPHYLAXIS 

of  the  wheel  apphed  down  in  the  fissures  of  the  molars  and  bicuspids. 
The  Dunn  cheek-distender  should  always  be  used.    It  is  almost  unnec- 


FiG.  172 


essary  to  state  that  the  sticks,  the  pumice,  the  floss  and  the  brush 
wheel  should  not  be  used  a  second  time.  Figs.  172  and  173  show  the 
adaptation  of  this  wheel. 


Fig.  173 


Children. — In  the  prophylactic  treatment  of  children  it  is  seldom 
necessary  to  use  the  instruments.  As  it  is  the  roots  of  the  teeth  that 
are  most  susceptible  to  disease  in  adults,  so  are  the  approximal 
surfaces  most  susceptible  in  children.     These  surfaces  should  be  care- 


BRUSHING  339 

fully  polished  with  the  floss  and  piuniee,  and  the  fissures  in  the  masti- 
eating  surfaees  with  the  Inrush  wheel  in  the  engine.  The  polishing 
of  all  the  surfaces  of  the  teeth  with  the  sticks  should  be  done  as 
described  for  the  adult.  In  order  to  assist  in  the  removal  of  the 
green  stains  on  the  surfaces  of  the  teeth  at  the  first  treatment  a  small 
napkin  may  be  used  to  dry  the  teeth,  and  a  pledget  of  cotton  soaked 
with  Churchill's  compound  tincture  of  iodin  applied  to  the  stains  and 
allowed  to  penetrate  them.  It  is  sometimes  necessary  to  make  a 
second  application  of  the  iodin  after  the  first  thorough  polishing,  but 
after  the  teeth  have  been  thoroughly  polished  and  the  patient  is 
coming  at  regular  intervals  for  these  surface  treatments,  no  further 
use  of  the  iodin  will  be  necessary.  Attention  is  called  to  a  preventive 
treatment  of  the  fissures  in  the  first  permanent  molars  of  children  that 
comes  within  the  province  of  the  dental  hygienist. 

When  these  fissures  are  found  to  be  exceptionally  deep,  likely  to 
retain  food  debris  and  thus  susceptible  to  decay,  a  quick-setting,  hy- 
draulic cement  should  be  mixed,  and  with  cotton  rolls  on  each  side 
of  the  tooth,  the  fissures  should  be  dried  with  warm  air,  and  washed 
with  a  pledget  of  cotton  soaked  with  alcohol,  again  dried  and  then 
with  an  explorer  the  soft  cement  worked  down  into  the  fissures.  As 
the  cement  begins  to  toughen  and  set,  the  end  of  the  second  finger  is 
dipped  in  a  glass  of  water  and  with  the  ball  of  the  finger  the  cement  is 
pressed  firmly  down  into  the  fissure  and  held  there  for  a  moment  or 
two  until  it  has  become  fairly  hard.  The  surplus  can  easily  be  trimmed 
away  and  the  cement  in  the  fissures  will  last  for  some  time,  acting  as 
a  protection  to  theu'  sm-faces.  It  takes  but  a  short  time  to  renew  it 
when  it  wears  away,  and  will  frequently  save  these  teeth  from  decay 
at  the  susceptible  period  of  from  six  to  twelve  years  of  age. 

BRUSHING. 

Because  a  remarkable  condition  of  health  and  beauty  of  the  gums 
and  a  high  resistance  and  increased  vitality  of  the  peridental  membrane 
may  be  developed  by  the  proper  form  of  brushing,  it  may  be  well  to 
consider  first  the  blood  supply  to  the  peridental  membrane  and  how 
its  vitality  may  be  greatly  increased  by  establishing  fast  and  perfect 
circulation  in  the  gum  tissue  itself. 

Plate  VII  illustrates,  diagramatically,  the  blood  supply  to  the  peri- 
dental membrane  of  a  tooth.  The  small  arteries  entering  the  apical 
space  break  up  into  branches,  one  or  more  of  them  enter  the  pulp 
canal  through  the  apex  of  the  root,  and  the  others  pass  down  between 
the  fibers  of  the  peridental  membrane.  During  their  course  through 
the  membrane  on  their  way  to  the  alveolar  border  and  the  gum  tissue 
they  both  give  off  and  receive  branches  through  the  alveolus  and  connect 
with  the  plexus  of  small  bloodvessels  and  capillaries  of  the  gum  tissue. 

It  wull  thus  be  readily  seen  that  the  blood  circulation  in  the  gums  is 
very  intimately  associated  with  the  peridental  membrane.     It  fre- 


340  DENTAL  PROPHYLAXIS 

queiitly  happens  that  when  an  alveolar  abscess  develops  at  the  apex  of 
the  root  of  a  tooth,  these  bloodvessels  in  the  apical  space  are  destroyed, 
yet  the  peridental  membrane  does  not  sufi'er  from  lack  of  blood,  for 
the  branches  coming  to  it  from  the  walls  of  the  alveolus  soon  enlarge 
and  produce  a  sufficient  supply.  It  must  therefore  be  noted  that 
in  order  to  stimulate  the  blood  supply  of  the  peridental  membrane 
it  is  merely  necessary  to  stimulate  circulation  in  the  gum  tissue.  Fibers 
of  the  peridental  membrane  radiate  out  into  the  gum  tissue  and  strong 
bands  of  fibers  which  form  the  dental  ligament  blend  into  the  peri- 
osteum of  the  alveolar  process.  Because  some  of  these  fibers  are  so 
close  to  the  surface  in  the  gum  tissue  it  is  not  difficult  to  under- 
stand why  an  unusual  response  to  health  may  be  obtained  by  surface 
stimulation. 

In  the  process  of  masticating  coarse  foods  a  natural  massage  takes 
place  in  the  following  manner:  The  teeth,  being  occluded  with  con- 
siderable force,  are  pressed  down  in  their  sockets.  The  peridental 
membrane  is  thus  compressed  and  the  blood  is  squeezed  out  of  the 
small  bloodvessels.  As  the  jaws  open  and  release  the  pressure  on  the 
teeth,  the  pressure  on  the  small  bloodvessels  in  the  membrane  is  also 
released  and  the  blood  comes  rushing  in  again. 

This  pressure  and  release  is  similar  in  its  action  to  a  massage  of  the 
tissues  on  the  surface  of  the  body.  The  coarse  foods  sliding  over  the 
surfaces  of  the  teeth  press  upward  on  the  upper  gums  and  downward 
on  the  lower  gums.  This  pressure  and  release  on  the  bloodvessels  in 
the  gum  tissue  acts  in  the  same  manner  as  that  on  the  peridental  mem- 
brane. Such  a  process  always  stimulates  a  free  flow  of  blood  and  pre- 
vents congestion  or  stasis  in  the  capillary  circulation. 

Keratin. — In  the  basement  layer  of  the  skin,  cells  are  constantly 
being  formed  and  forced  slowly  upward  toward  the  surface  of  the  body. 
During  their  transit  the  cells  slowly  change  their  shape,  becoming  long 
and  flat  in  appearance  and  finally  form  the  pavement  or  squamous 
type  of  epithelum  on  the  surface  of  the  skin.  During  this  period,  from 
the  time  of  formation  to  their  arrival  on  the  surface  of  the  body,  a 
gradual  metamorphosis  or  change  takes  place  in  the  protoplasm  of 
the  cell.  Slowly  the  contents  of  the  cell  begins  to  toughen  and  this 
process  continues  just  in  proportion  to  the  needs  of  protection  against 
undue  friction  or  exposure.  The  horny  hands  of  the  day  laborer,  or 
the  corns  that  form  on  the  feet,  are  exami^les  of  the  extreme  expression 
of  the  activity  and  change  in  these  cells.  The  contents  of  the  cells 
when  so  changed  or  toughened  is  known  as  keratin. 

The  mucous  membrane  of  the  mouth  is  but  a  continuation  or  an 
infoUling  of  the  skin.  Its  epithelium  is  of  the  squamous  type  similar 
to  that  of  the  skin.  If  the  gum  tissue  is  artificially  stimulated  three 
or  four  times  a  day  with  the  bristles  of  the  tooth-l)rush,  a  noticeable 
change  takes  place  in  the  texture  of  the  mucous  membrane.  It  soon 
loses  that  smooth,  glassy  or  slazy  appearance  and  under  a  magnify- 
ing glass  shows  a  thickened  or  toughened  surface  which  seems  to  act 


BRUSHING  341 

as  a  protective  armor  for  tlie  underlying  tissues  and  makes  the  ingress 
of  infection  tiu-ough  tiie  gum  tissue,  or  at  the  gingiva',  extremely  diffi- 
cult. Inference  should  not  be  made  that  there  is  produced  a  hornified 
mucous  membrane,  except  in  a  modified  sense,  but  a  beneficial  change 
takes  place  that  is  much  to  be  desired.  A  similar  texture  of  membrane 
may  be  found  in  the  mouths  of  carnivorous  animals. 

The  Gums. — In  considering  the  health  of  these  dentinal  tissues  the 
gums  found  in  the  average  mouth  should  first  be  noted.  Aside  from 
the  unsanitary  aspect  of  the  crowns  of  the  teeth,  the  gums  will  be 
found  to  be  of  a  deep  red  color,  the  gingiva  usually  showing  even  a 
deeper  red.  The  blood  is  almost  stagnant  on  some  of  the  margins, 
and  the  tissues  will  bleed  upon  the  slightest  touch.  Waste  products 
are  not  being  properly  eliminated,  oxidation  is  imperfect  and  blood 
serum,  which  contains  the  lime  salts  for  serumal  deposits,  oozes  in 
the  subgingival  sj)aces  and  forms  an  ideal  mediiun  for  bacteria.  These 
are  the  average  gums  of  adults,  who  eat  food  which  requires  but  little 
mastication  and  produces  but  little  friction  on  the  gums,  and  who 
take  scant  care  of  their  mouths.  But  how  quickly  all  of  these  con- 
ditions will  change  under  artificial  stimulation.  The  instant  the  gums 
are  brushed  properly,  the  blood  starts  to  flow  more  rapidly  and  a  new 
life  and  color  make  their  appearance.  After  a  thorough  prophylactic 
treatment  and  a  lesson  in  gum  brushing  it  is  not  unusual  to  see  the 
tissues  lighten  in  color,  possibly  two  or  three  shades  in  twenty-four 
hours.  At  the  end  of  a  week  or  ten  days  they  assume  a  still  lighter 
shade  and  after  periods  ranging  from  three  to  six  months  they  become 
a  light  coral  pink,  and  hold  this  color  as  long  as  they  are  daily  brushed 
and  stimulated. 

There  is  apparently  a  peculiar  pink  shade  that  practically  every 
individual  may  acquire  if  the  brushing  is  faithfully  followed.  In  fact 
this  color  may  be  taken  for  so  sure  an  index,  that  it  is  easy  to  tell  at  a 
glance  whether  the  patient  has  been  brushing  the  teeth  and  gums  four 
times  daily  or  not.  Virtue,  in  this  case,  has  its  own  reward,  for  the  color 
is  always  obtained  when  the  brush  has  been  used  according  to  rule. 
The  gums  should  be  of  uniform  color  in  all  parts  of  the  mouth,  the  gin- 
givjp  showing  no  difference  in  shade  from  that  of  the  body  of  the  gum. 

Tissue  Stimulation. — If  the  following  rules  are  honestly  observed  the 
same  results  are  assured  in  every  mouth: 

1.  The  form  of  brushing  as  described  in  tliis  chapter. 

2.  Brushing  long  enough — not  less  than  two  minutes. 

3.  Brushing  four  times  a  day. 

Many  cases  have  been  baffling  because  they  would  not  respond  to 
treatment,  but  when  the  patient  gives  a  demonstration  at  the  wash 
bowl,' it  will  show  that  he  makes  some  omissions  or  uses  an  incor- 
rect form  of  brushing  which,  when  corrected,  will  bring  results  in  a 
short  time.  Sometimes  patients  will  claim  to  have  followed  the  rules 
when,  upon  close  investigation,  it  will  be  found  that  they  have  not 
done  so. 


342  DENTAL  PROPHYLAXIS 

^Yhen  the  gum  tissue  -will  not  assume  this  hght  pink  shade  in  six 
months'  time,  and  when  the  patient  is  expert  with  the  tooth-brush  and 
claims  to  follow  the  rules  faithfully,  it  may  be  suspected  that  in  some 
way  the  rules  are  not  lived  up  to  or  that  otherwise  a  very  rare  excep- 
tion has  been  found. 

Evidently  this  color  that  the  gums  assume  under  the  daily  brushing 
is  due  to  the  fast  flow  of  blood  through  the  capillaries,  the  perfect 
oxidation  of  the  cells  and  thorough  removal  of  their  waste  products, 
as  well  as  a  thickening  or  toughening  of  the  epithelial  layer  of  cells  on 
the  siu-face.  The  festoons  become  pink  and  tough,  the  surface  of  the 
mucous  membrane  loses  its  thin,  glassy  appearance,  and  when  dried 
looks  tough  and  firm.  Also  when  the  edges  of  the  gum  are  dried  they 
do  not  weep.  Little  or  no  serum  oozes  now  from  this  tissue  and  it 
will  be  noted  that  the  serumal  deposits,  found  so  plentifully  under  the 
congested  borders  of  the  gums,  almost  entirely  disappear  at  subsequent 
treatments.  It  must  not  be  assumed  that  the  miraculous  happens  under 
these  unusual  health  conditions  or  that  merely  learning  how  to  brush 
the  gums  will  eliminate  all  present  and  future  disease  of  the  mouth. 
This  is  not  so,  but  one  cannot  help  being  enthusiastic  when  one  sees  so 
many  returns  to  health  of  the  dentinal  tissues  under  stimulation.  The 
peridental  membrane  seems  to  acquire  new  life,  and  apparently  feels 
the  stimulation  in  every  fiber  and  cell.  Loose  and  sore  teeth  become 
tight  and  free  from  soreness,  providing  that  too  much  of  their  support- 
ing tissue  has  not  been  lost.  Chronic  cases  of  pericementitis  disap- 
pear and  even  the  pulp  itself  may  be  relieved  of  congestion  if  it  is  slight 
and  has  not  progressed  too  far.  There  is  no  doubt  but  that  the  osteo- 
blasts, under  prophylaxis  and  this  stimulation,  do  at  times  replace 
small  areas  of  lost  alveolar  process.  Where  roots  have  been  exposed 
on  the  labial  or  approximal  surfaces,  especially  those  of  the  incisors 
and  cuspids,  it  is  not  uncommon  to  see  gum  tissue  creep  back  over 
the  exposed  root  to  a  considerable  degree  and  on  approximal  surfaces 
there  has  been  a  filling  in  of  the  bony  tissue  to  support  the  gum  which 
is  undoubtedly  a  new  deposit  of  process.  When  it  is  considered  that 
the  osteoblasts  are  present  in  the  peridental  membrane  throughout 
life  and  slowly  add  to  the  alveolar  wall  of  the  socket,  it  is  not  unreason- 
able to  expect  them  to  lend  their  aid  when  stimulated  and  the  irritat- 
ing cause  removed. 

Fig.  174  illustrates  what  gum  brushing  will  do.  All  the  teeth  in 
this  mouth  were  affected  by  pyorrhea.  They  were  loose  and  the  left 
central  found  to  })e  beyond  saving.  The  gums  are  a  light  coral  pink, 
the  teeth  firm  and  for  nearly  thirteen  years  there  has  been  no  percep- 
tible change  in  absorption  or  recession. 

Fig.  175  shows  the  result  of  a  case  of  acute  gingivitis.  This  occurred 
eight  years  ago,  and  the  exposed  surface  of  the  root  at  the  time  was 
nearly  a  third  longer.  By  proj)hylaxis  and  ginn  stimulation  a  portion 
of  the  root  was  covered  by  new  gum  tissue.  There  has  been  no  change 
in  the  intervening  eight  years. 


BRUSHING 


343 


Fig.  176  shows  the  right  cuspid  in  the  mouth  of  the  same  patient. 
This  gum  was  also  affected  by  acute  gingivitis  and  the  root  was  exposed 


Fig.  174 


Fig.  175 


Fig.  176 


344 


DENTAL  PROPHYLAXIS 


nearly  an  eighth  of  an  inch  before  the  inflammation  dissappeared. 
There  was  undoubtedly  a  replacement  of  lost  tissue  here  and  it  has 
proved  to  be  very  stable. 

Fig.   177  shows  another  case  of  the  destructive  process  of  acute 
gingivitis.    Eleven  years  ago  the  indications  were  that  this  tooth  could 


Fig.  177 

not  be  saved.  The  apex  was  nearly  exposed  and  a  larger  area  of  the 
root  uncovered.  The  gum  tissue  is  now  hard  and  pink  and  the  tooth 
firm  and  useful. 

Fig.  178  is  a  similar  case  but  a  year  old.  The  conditions  are  bad,  as 
the  space  between  the  lateral  and  central  will  not  permit  of  thorough 
cleansing  without  much  efl'ort.  There  has  been  a  replacement  of  con- 
siderable tissue,  the  teeth  have  tightened  and  can  no  doubt  be  retained 
for  some  time  to  come. 


Fig.  178 


It  seems  probable  that  it  is  not  only  possible  to  sterilize  tissue  by 
this  active  hyj)eremia,  artificially  induced,  but  also  that  small  serumal 
deposits  may  be  dissolved  and  disposed  of  by  the  blood  or  possibly 
by    the   action    of  the   cells  in  these  tissues.     This  statement  does 


BRUSHING  345 

not  mean  that  when  the  dental  surgeon  treats  a  case  of  pyorrhea 
alveolaris,  that  merely  teaching  the  patient  how  to  brush  his  gums  will 
cause  the  dissolution  of  the  dei)osits  and  kill  the  infection.  It  means 
that  it  is  exceedingly  important  that  gum  brushing  should  be  taught 
and  the  patient  trained  by  repeated  lessons  until  he  acquires  this  art, 
for  it  really  is  an  art.  With  the  additional  aid  of  the  gum  brushing 
the  pus  will  soon  cease,  the  pockets  will  contract  and  close,  soreness 
will  be  relieved  and  any  small  granular  deposits  that  may  be  left  will 
gradually  disappear  as  the  tissue  hugs  up  tightly  to  the  root.  The 
tisslies,  thus  artificially  stimulated,  seem  to  possess  five  properties, 
analgesic,  bactericidal,  absorbent,  solvent  and  nutritive.  The  analgesic 
effect  is  no  doubt  produced  by  the  relief  of  tension  and  toxic  influence. 
Whether  the  bactericidal  effect  is  one  of  phagocytosis  or  of,  opsonins 
is  immaterial.  There  is  no  question  but  that  when  cleanliness  is 
established  and  the  tissues  regularly  stimulated  by  brushing,  the 
infection  is  destroyed.  The  absorption  in  the  tissues  is  accomplished, 
not  only  by  the  lymphatics  but  by  the  capillaries  themselves.  It  is  a 
well-known  fact  that  a  ligature  of  catgut  in  the  body  is  dissolved  and 
disappears.  Landois  has  shown  that  the  blood  serum  of  every  animal 
has  the  power  of  dissolving  the  blood  corpuscles  from  a  different 
species.  Where  or  how  this  solvent  originates  that  causes  the  disap- 
pearance of  the  small  granules  of  serumal  deposits  can  only  be  con- 
jectured. Induced  active  hyperemia  will  demonstrate  that  they  do 
disappear.  The  nutritive  property  is  self-evident,  and  is  due  chiefly 
to  a  perfect  oxidizing  process.  There  is  still  much  to  learn  concerning 
these  artificial  stimulants.  If  the  existence  of  human  beings  were 
more  like  that  of  animals,  this  condition  would  be  induced  each  time 
that  the  meal  of  coarse  food  was  chewed.  Since  the  artificial  rather 
than  the  animal  life  is  preferred,  and  coarse  food  is  not  attractive, 
why  should  not  this  condition  of  health  be  produced  artificially? 

Tooth-brushes. — Opinions  vary  greatly  concerning  the  size  and  shape 
of  the  tooth-brush.  One  educator  of  the  middle  West  states  in  a  letter 
that  he  did  not  recommend  a  hair-brush,  a  nail-brush  or  a  shoe-brush 
for  brushing  the  teeth,  but  a  tooth-brush.  His  position  might  have 
received  serious  consideration  if  it  were  only  the  crowns  of  the  teeth 
that  were  involved,  but  as  the  brushing  of  the  gums  is  of  equal  impor- 
tance with  brushing  the  teeth,  a  brush  that  will  adapt  istelf  to  both 
surfaces  is  the  one  to  use. 

Again,  if  cross  brushing  is  indulged  in  or  a  slow  twisting  massage 
or  wiping  motion  is  employed,  the  form  and  size  of  the  brush  may  be 
varied.  Personally,  the  AATiter  has  not  been  able  to  secure  as  satis- 
factory results  with  either  of  these  forms  of  brushing.  The  cross  brush- 
ing seems  to  irritate  the  festoons,  at  times  will  create  absorption,  and 
lacks  the  cleansing  action  upon  the  outside  surfaces.  The  wiping 
motion  with  the  sides  and  ends  of  the  bristles  is  more  cleansing  and 
the  gums  take  more  kindly  to  this  form  of  brushing,  but  when  it  is  con- 
sidered that  nature  intended  that  the  pressure  should  be  chiefly  upward 


346 


DENTAL  PROPHYLAXIS 


on  the  upper  gums  and  do^Muvard  on  the  lower  gums,  such  as  is  induced 
by  food  shding  over  the  sm'faces  of  the  teeth  in  mastication,  it  can  be 
seen  that  this  process  can  be  better  simulated  by  a  rotary  stroke  than 
by  any  other  way.  The  gums  appear  to  thrive  under  the  rotary  stroke, 
a  stimulus  is  imparted  to  the  circulation  and  a  thorough  cleansing 
effect  is  produced  along  the  curved  lines  of  the  festoons  and  upon  a 
third  of  the  approximal  surfaces.  A  slow^  deliberate  stroke  is  not  as 
stimulating  as  a  fast,  light  stroke.  The  best  way  to  bring  blood  to  the 
sm-face  of  a  tissue  in  a  short  space  of  time  is  to  use  a  light,  rapid  massage. 
The  results  will  justif}"  the  means,  so  a  rotary  stroke  for  the  buccal 
and  labial  surfaces  is  advised.  In  order  to  secure  the  proper  adaptation 
of  a  brush  to  the  surfaces  of  the  gums  and  the  teeth,  the  shape  of  the 
bristle  ends  of  the  brush  is  important.  Many  of  the  popular  brushes 
on  the  market  are  nearly  concave  in  shape,  having  a  long  toe  and  heel 
with  the  shorter  bristles  near  the  center.  Such  a  brush,  placed  squarely 
across  the  front  teeth,  seems  to  fit  when  at  rest,  but  if  slowly  moved 
about  the  mouth,  it  will  be  found  to  ride  in  many  places  on  the  toe 


Fig.  179 


and  heel  alone  or,  if  pressure  is  used,  these  long  bristles  ride  sidewise 
or  any  other  way.  Although  the  cranium  is  convex  in  shape,  it  has 
never  been  deemed  expedient  to  use  a  concave  hair-brush.  In  fact, 
a  concave  brush  would  not  be  as  effective  as  a  straight  one,  although  it 
might  seem  to  fit  better  when  at  rest.  Apparently  a  straight-cut  tooth- 
brush with  a  slight  tuft  on  the  end  is  best  adaj^ted  to  most  of  the  sur- 
faces in  most  mouths.  The  bristles  should  be  of  sufficient  length  to 
be  flexible  yet  springy  and  stiff  enough  not  to  lose  their  life  or  spring 
after  the  first  two  or  three  days'  use.  This  necessitates  using  a  brush 
with  bristles  a  trifle  hard,  for  such  a  brush  becomes  softened  after  a 
few  days'  use.  Fig.  179  illustrates  the  two  shapes  of  brushes  just 
referred  to.  When  instructing  a  new  patient  in  the  art  of  brushing,  a 
soft  brush  should  be  recommended  to  start  with,  otherwise  the  patient 
should  be  warned  not  to  be  too  strenuous  with  the  stifl"  brush  until  the 
gums  have  had  a  chance  to  become  tough. and  the  mucous  membrane 
thickened,  otherwise  slight  abrasions  of  the  mucous  membrane  will 
be  produced,  and  a  sore  and  tender  surface  will  result  if  the  gums  are 


BRUSHING 


347 


brushed  at  first  with  too  much  pressure  and  vigor  and  with  a  stiff 
brush. 

Instructions  for  Brushing. — The  process  of  the  brushing  of  the  gums 
and  the  teeth  may  be  divided  into  three  parts: 

First,  the  outside  or  buccal  and  labial  surfaces. 
Second,  the  inside  or  palatal  and  lingual  surfaces. 
Third,  the  occlusal  or  masticating  surfaces  of  the  teeth. 
The  Buccal  and  Labial  Surfaces. — "With  the  brush  held  in  the  hand,  as 
in  Fig.  180,  and  with  the  teeth  nearly  closed,  the  brush  is  placed  inside 
the  cheek  on  the  left  side,  so  that  the  ends  of  the  bristles  are  lightly 
•  in  contact  with  the  gums  over  the  upper  molars.     Now,  with  a  fast, 
circular  motion  the  brush  is  swept  backward  and  downward,  reaching 


Fig.  180 


as  far  down  on  the  lower  gums  as  the  brush  can  travel  in  this  posi- 
tion, then  forward  and  upward  as  high  on  the  gums  of  the  upper 
teeth  as  possible  (Fig.  181). 

The  brush  should  travel  in  a  perfect  circle,  not  in  an  oblong  tract, 
and  in  as  large  a  circle  as  the  vestibule  of  the  cheek  will  permit. 
Very  little  pressure  should  be  used,  for  the  stimulating  as  well  as  the 
cleansing  process  is  accomplished  by  the  rapidity  of  the  stroke  and  the 
direction  traveled  by  the  ends  of  the  bristles.  Continuing  this  fast, 
circular  motion  the  brush  should  be  made  to  travel  very  slowly  for- 
ward until  the  heel  of  the  brush  engages  the  right  cuspids.  Pausing 
on  the  incisors  to  stimulate  thoroughly  the  gums  on  both  jaws,  start 
back  again  slowly  to  the  region  of  the  molars  (Fig.  182). 


348 


DENTAL  PROPHYLAXIS 


It  will  be  understood  that  the  brush  is  constantly  in  motion,  travel- 
ing in  a  large  circle  with  the  ends  of  the  bristles  lightly  touching  the 
gums  and  teeth  with  as  rapid  a  motion  as  possible. 


Fig.  181 


Fig.  183  illustrates  the  position  of  holding  the  brush  for  the  right 
side.     On  this  side  some  persons  find  it  easier  to  maintain  a  circular 


I'l.;.  182 


motion  by  reversing  the  stroke,  or  brushing  from  the  lower  gums  back- 
ward and  upward.    It  makes  no  difference  in  which  direction  the  brush 


BRUSHING 


349 


travels  as  long  as  the  circular  stroke  is  adhered  to.    Assuming  that  one 
is  using  the  right  hand  for  brushing,  it  will  not  be  possible  to  brush 


Fig.  183 


farther  forward  than  the  right  cuspid  teeth  (Fig.  184).    Directions  for 
brushing  the  left  side  are  applicable  to  the  right. 


Fig,  184 


Lingual  Surfaces. — 1.   Uj^per.     The  brush  should  be  held  as  shown 
in  Fig.  185.    The  roof  of  the  mouth  as  well  as  the  lingual  surfaces  of 


350 


DENTAL  PROPHYLAXIS 


the  upper  teeth  are  brushed  with  an  in-and-out  stroke,  as  in  Fig.  186. 
The  ends  of  the  bristles  should  be  placed  against  the  gums  of  the  right 


Fig.  185 


molar  teeth,  and  the  brush  drawn  straight  forward  until  the  heel  of 
the  brush  (the  last  bristles  nearest  the  hand  are  called  the  heel)  wipes 
the  lingual  surfaces  of  the  right  incisors  and  cuspids  and  protrudes 
from  the  mouth  for  a  short  distance.    The  upper  lip  should  be  drawn 


Fig    18G 


downward  to  prevent  the  moisture  from  being  thrown  outward  by  the 
snap  of  the  bristles  passing  over  the  edges  of  the  incisors.    The  brush  is 


BRUSHING 


351 


now  pushed  straight  back  again  on  the  gums  and  this  in-and-out  stroke 
is  rapidly  made  and  confined  on  this  surface  for  a  few  seconds.  This 
fast  in-and-out  stroke  of  the  brush  is  kept  up  and  carried  across  the 
roof  of  the  mouth  until  all  of  the  hard  palate  is  covered  and  the  gums 
on  the  left  side  of  the  mouth  are  reached.  Here  the  in-and-out  stroke 
is  applied  rapidly  for  a  few  seconds,  as  far  back  as  the  distal  surfaces  of 
the  third  molars.  The  same  stroke  should  be  used  on  the  return,  the 
palate  should  be  crossed  to  the  right  side  again,  and  again  back  to 
the  left  side.  Special  care  should  be  used  to  reach  the  gums  around 
the  last  molars,  there  is  a  tendency  not  to  brush  back  far  enough. 

2.  Lower  Linr/nal  Surfaces. — The  lingual  surfaces  of  the  lower  teeth 
are  the  most  difficult  to  brush  and  it  takes  quite  a  little  practise  before 


Fig.  187 


the  gums  can  be  deftly  reached,  especially  on  the  right  side.  Nineteen 
out  of  twenty  mouths  will  disclose  a  congested  gingival  border  on 
the  lingual  surfaces  of  the  right  molars,  and  in  order  that  the  wrist 
may  bend  freely  so  that  the  toe  of  the  brush  may  reach  this  surface, 
it  is  suggested  that  the  brush  be  held  in  the  hand  as  in  Fig.  1S7. 

These  gum  surfaces  are  brushed  almost  entirely  with  the  toe  or  tuft 
of  the  brush,  the  motion  being  a  fast  in-and-out  stroke,  similar  to  that 
used  on  the  hard  palate,  as  in  Fig.  188.  Starting  on  the  right  side  with 
the  bristles  of  the  tuft  resting  on  the  gum  next  to  the  last  molar,  the 
brush  is  drawn  forward.  In  this  case  the  bristles  at  the  heel  do  not 
sweep  the  lower  incisors  as  the  handle  of  the  brush  is  tipped  slightly 
upward,  so  that  the  brushing  is  done  almost  entirely  with  the  tuft. 

The  brush  is  now  forced  backward  in  the  same  line,  leaning  slightly 


352 


DENTAL  PROPHYLAXIS 


toward  the  tongue,  and  the  in-and-out  stroke"  is  appHed  rapidly  to 
this  surface.  jNIaintaining  always  this  fast  stroke,  and  slowly  coming 
forward,  the  handle  of  the  brush  is  now  raised  to  a  sharp  angle  and  the 
gums  below  the  incisors  are  brushed  with  an  up-and-down  stroke, 


^^^^^^^H^T 

m 

W^ 

I^^^B 

a 

'^^1 

1 

[^9 

HT^f;'^         /'' 

i 

^ 

!ttL^B..-*^4^^^^l 

Fig.  188 


going  back  and  forth  across  them  several  times.  Continuing  the  in- 
and-out  stroke  the  tuft  is  adapted  to  the  gums  of  the  left  side  and  they 
are  brushed  in  a  manner  similar  to  that  described  for  the  right  side, 
again  slowly  returning  to  the  right  and  repeating  once  more  to  the  left 
side.    A  slight  gagging  sensation  will  sometimes  be  felt  in  trying  to 


Fig.  189 


reach  as  far  back  as  the  brush  should  actually  go,  but  with  persistent 
practise  this  can  be  greatly  overcome  in  a  short  time. 

Masticating    Surfaces. — Lastly  the  masticating   surfaces   should   be 
brushed  in  order  to  remove  any  food  debris  in  the  fissures  or  sulci  of 


BRUSHING  353 

the  molars  and  bicuspids.  The  tuft  of  the  l)rush  sliould  also  be  carried 
to  the  flistal  surfaces  of  the  last  molars  on  both  the  upper  and  lower 
jaws  and  with  a  wiping  or  twisting  motion  these  surfaces  should  be 
cleansed. 

The  foregoing  description  of  brushing  gives  but  a  stereotyped  form. 
The  mouth  should  be  gone  over  three  or  four  times  until  the  gums 
begin  to  tingle  and  a  slight  sense  of  numV)ness  is  felt. 

The  festoons  on  the  palatal  and  lingual  surfaces  cannot  be  properly 
brushed  with  the  circular  stroke.  It  may  be  noted  that  they  assume 
a  much  straighter  line  than  on  the  buccal  surface  and  that  the  bristles 
traveling  in  and  out  with  this  straight  line  reach  all  surfaces  and  are 
more  stimulating  and  non-irritating  in  their  action. 

In  the  roof  of  the  mouth  are  the  posterior  and  anterior  palatine 
arteries  which  help  to  supply  the  gum  tissue,  hence  the  importance  of 
brushing  the  hard  palate  (Fig.  189). 

It  should  be  noted  that  the  brush  is  used  with  a  full-arm  motion 
and  that  a  fast  but  light  stroke  is  essential  to  secure  the  desired  results. 

Number  of  Daily  Brushings. — Not  so  very  many  years  ago  more  than 
one  bathtub  in  a  private  house  was  considered  a  luxury.  Today  it 
is  realized  that  frequent  bathing  is  a  necessity. 

Some  dentists  advise  their  patients  to  brush  their  teeth  before 
retiring;  some,  night  and  morning;  and  the  patient  who  followed  tliis 
last  rule,  thought  himself  virtuous  indeed.  The  matter  of  brushing 
the  teeth  is  piu"ely  educational  and  resolves  itself  into  a  habit.  Time 
can  always  be  found  for  any  habit— it  is  merely  a  question  of  what 
habits  are  acquired. 

After  each  meal  a  certain  amount  of  food  is  retained  on  the  surfaces 
of  the  teeth.  .  In  less  than  an  hour's  time  this  food  begins  to  decom- 
pose. If  the  teeth  are  brushed  at  night  and  in  the  morning  before 
breakfast,  remnants  of  the  breakfast  remain  on  the  teeth  until  bed- 
time, joined  through  the  day  by  those  of  lunch  and  dinner.  There 
may  be  some  arguments  in  favor  of  not  disturbing  the  decomposing 
food  in  the  mouth  all  day,  but  such  arguments  are  usually  based  on 
the  statement  that  people  do  live  wdth  unbrushed  teeth,  so  why  handi- 
cap them  with  an  extra  daily  duty  when  they  have  so  little  time  to 
spare.  Those  who  advance  these  arguments  usually  have  a  breath 
far  from  pleasing.  It  cannot  be  shown  scientifically  that  a  mouth 
containing  decomposing  food  is  as  healthy  and  wholesome  as  one  that 
is  free  from  it. 

The  teeth  should  be  thoroughly  cleaned  after  each  meal  with  brush 
and  dentifrice,  and  given  a  vigorous  brushing  with  clear  water  the 
first  thing  in  the  morning.  This  means  four  brushings  a  day.  Of  course 
it  is  not  always  possible  to  follow^  this  rule  to  the  letter,  but  where 
one  has  access  to  a  bowl  and  one's  tooth-brush,  the  teeth  should  be 
cleaned.  All  children  should  be  taught  this  habit,  as  there  can  be  no 
greater  insurance  for  health  and  freedom  from  infectious  diseases 
than  a  mouth  free  from  decomposing  food. 
23 


354  DENTAL  PROPHYLAXIS 

Dentifrices. — The  most  important  ingredient  in  a  dentifrice  is  soap. 
Next,  a  slight  abrasive,  such  as  a  fine  grade  of  precipitated  chalk. 
The  rest  of  the  formula  is  of  but  little  value  and  is  used  chiefly  to  dis- 
guise the  soap  and  impart  a  pleasant  taste.  The  removal  of  grease  is 
a  chemical  action  and  soap  is  essential  for  thoroughly  cleaning  the 
teeth.  If  fat  is  rubbed  on  the  hands  or  on  a  slab  of  glass  it  will  be 
difficult  to  remove  it  with  clear  water  and  a  brush.  Although  with 
considerable  effort  it  may  be  done,  soap  will  remove  it  much  more 
quickly.  A  fine  grade  of  powdered  Castile  soap  is  the  best,  but  it  is 
seldom  found  in  the  preparations  on  the  market,  as  it  does  not  give 
sufficient  lather  to  suit  either  manufacturer  or  purchaser.  The  most 
harmful  element  in  a  dentifrice  is  the  use  of  cheap  coarse  grades  of 
chalk.  In  fact  some  preparations  contain  pumice  and  in  one  foreign 
■production,  powdered  oyster  shells  were  found.  The  teeth  should  be 
cleaned,  not  scoured,  and  the  daily  use  of  a  gritty  dentifrice  will  even- 
tually cause  abrasion  of  the  thin  enamel  surfaces  at  the  necks  of 
the  teeth.  The  grit  may  be  readily  detected  by  placing  some  of  the 
paste  or  powder  between  the  teeth  and  biting  on  it.  Finer  tests  may 
be  made  by  putting  it  between  two  glass  surfaces,  rubbing  them  to- 
gether and  examining  them  with  a  magnifying  glass. 

A  slight  abrasive  is  helpful  in  aiding  in  the  removal  of  the  slippery 
film  of  mucin  and  viscid  accretions  on  the  surfaces  of  the  teeth.  Its 
daily  use  is  harmless  providing  the  grit  is  fairly  soluble  and  not  coarse. 
^Nhen  one  computes  the  number  of  occlusions  that  take  place  daily 
between  the  masticating  surfaces  of  the  teeth  diuing  the  three  meals 
and  notes  what  little  wear  of  the  enamel  cusps  is  exhibited  at  thirty- 
five  or  forty  years  of  age,  it  may  be  concluded  that  the  use  of  a  fine 
grade  of  precipitated  chalk  as  a  base  for  a  dentifrice  is  not  a  serious 
menace  to  the  enamel  tissues.  There  is  but  little  choice  between  pow- 
der and  paste,  as  regards  efficiency.  Powder  has  to  be  worked  into  a 
paste-like  condition  in  the  mouth  with  the  brush,  while  paste  quickly 
spreads  itself  over  the  teeth  for  immediate  action.  The  majority  of 
people  find  the  paste  much  pleasanter  to  use.  The  difference  in  the 
formulae  of  the  two  preparations  consists  in  leaving  out  the  saccharin 
in  the  powder  and  mixing  the  powders  and  oils  with  glycerin  to  form 
paste. 

A  simple,  cheap  and  effective  powder  may  be  made  by  placing  the 
following  ingredients,  all  of  which  may  be  bought  at  any  drug-store, 
in  a  quart  Mason  jar: 

Finest  grade  English  precipitated  chalk 5  pound 

Powdered  Castile  soap If  ounces 

Light  carbonate  of  magnesia i  ounce 

Oil  of  clove 46    drops 

Oil  of  wintergreeu 35        " 

Oil  of  sassafras       . 35        " 

Oil  of  peppermint 18        " 

Saccharin — finely  powdered 4    grains 


BRUSHING 


355 


The  glass  top  should  be  securely  fastened  on  and  the  contents  shaken 
vigorously.  This  mixing  process  takes  some  time,  but  as  it  takes  at 
least  twenty-four  hours  for  the  oils  to  permeate  the  powders,  the  jar 
may  be  picked  up  at  varying  intervals  and  its  contents  thoroughly 
shaken.  A  larger  bottle  with  the  same  quantity  of  powder  will  permit 
of  a  more  thorough  mixing  in  a  shorter  time. 

The  brush  should  be  very  wet  when  the  powder  is  placed  upon  it 
and  care  should  be  taken  not  to  inhale  when  introducing  the  brush 
into  the  mouth. 

A  properly  prepared  tooth  paste  is  a  much  pleasanter  toilet  article 
to  use  and,  as  there  are  some  on  the  market  quite  effective  and  harm- 
less, one  of  these  may  be  recommended  to  patients  for  use. 

Each  tooth  has  five  surfaces.  Three  of  these  can  be  cleaned  with 
the  brush,  but  the  two  approximal  surfaces,  the  most  susceptible  of 
all,  cannot  be  reached  with  it.  In  other  words  three-fifths  of  the  sur- 
faces of  the  teeth  can  be  cleaned  with  the  tooth-brush  but  not  th(3 
remaining  two-fifths  which  most  need  it.  It  should  then  be  apparent 
that  if  all  the  food  is  to  be  cleaned  off  all  the  surfaces  of  all  the  teeth, 
additional  means  of  so  doing  must  be  employed  other  than  the 
tooth-brush.  Up  to  the  present  time  nothing  is  known  that  will  accom- 
plish this  more  efficiently  and  harmlessly  than  the  floss  silk  and  lime- 
water. 


Fig.  190 


Floss  Silk. — If  the  floss  silk  is  skilfully  and  frequently  used,  the 
approximal  surfaces  may  be  kept  quite  free  from  dental  caries.  To 
induce  patients  to  use  the  floss  silk  with  regularity  is  a  task,  but  by 
being  persistent  in  requesting  and  logical  in  the  reason  for  its  use,  they 
may  be  made  gradually  to  acquire  the  floss  habit.    To  insure  the  proper 


356 


DENTAL  PROPHYLAXIS 


use  of  the  floss  the  fiUings  in  the  approximal  surfaces  should  be  smooth 
and  poHshed,  with  just  sufficient  pressure  at  the  contact  points  to  allow 
the  floss  to  snap  through  without  too  much  effort  in  forcing  it.    Care 


Fig.  191 


should  also  be  taken  not  to  allow  the  floss  to  snap  through  on  the  gum 
tissue  hard  enough  to  wound  it.     There  is  but  little  danger  of  this 


Fig.  192 


after  a  little  j)ractise,  esi)('cially  after  the  gums  have  become  hard  and 
tough  from  brushing.  A  reasonably  sniall-si/ed  waxed  floss  is  the  best 
to  use.    For  adults  the  piece  should  be  fourteen  or  fifteen  inches  in 


BRUSHING 


357 


length.  The  end  of  the  floss  is  taken  between  the  thumb  and  first 
finger  of  the  left  hand  and  two  wrai)s  made  around  the  end  of  the  first 
finger,  and  this  act  repeated  with  the  other  end  of  the  floss  on  the 


Fig.  193 


Fig.  194 


358  DENTAL  PROPHYLAXIS 

right  forefinger.  The  floss  is  now  held  securely  and  will  permit  the 
ends  of  the  two  thumbs  or  the  two  second  fingers  or  a  combination  of 
a  thumb  of  one  hand  and  a  second  finger  of  the  other,  to  guide  the  silk 
into  its  position  in  the  mouth  and  force  it  between  the  teeth.  Fig. 
190  shows  adaptation  of  floss  for  right  upper  teeth.  Fig.  191  shows 
adaptation  for  left  upper  teeth.  Fig.  192  shows  adaptation  for  all 
the  lower  teeth.  After  the  floss  has  passed  through  the  contact  points 
it  should  be  rubbed  back  and  forth  against  both  approximal  surfaces 
to  polish  them  mechanically.  In  withdrawing  the  floss,  if  the  end  held 
opposite  the  lingual  surface  is  brought  over  on  the  buccal  surface  and 
the  silk  is  pulled  through  the  contact  points  in  the  form  of  a  loop,  it 
will  be  more  effective  in  polishing  or  cleaning  these  surfaces  than  if 
merely  snapped  out  (Figs.  193  and  194).  The  floss  will  not,  however, 
thoroughly  remove  all  the  food  between  the  teeth,  therefore  we  must 
have  recourse  to  a  mouth  wash. 

Lime-water. — Practically  all  the  mouth  washes  on  the  market  are 
formulated  to  accomplish  two  results.  First,  a  neutralizing  action, 
either  acid  or  alkaline,  and  second,  a  germicidal  action.  It  will  readily 
be  understood  that  the  latter  result  cannot  be  obtained  in  the  mouth, 
while  the  former  is  immaterial.  In  order  to  secure  immunity  to  decay, 
the  bacteria  must  be  robbed  of  any  pabulum,  upon  which  to  feed  and 
any  placques  or  glue-like  accumulations  on  the  surfaces  of  the  teeth 
must  be  dissolved. 

Acid  mouth  washes  have  been  advocated  because  it  has  been  found 
that  the  lactic  acid  forming  bacteria  are  retarded  in  their  growth  and 
activit}^  in  an  acid  medium.  Alkaline  washes  have  been  prescribed 
because  of  the  belief  that  they  will  neutralize  any  lactic  acid  formed 
that  will  induce  caries.  Both  of  these  theories  are  based  on  partial 
facts  only,  for  it  has  been  absolutely  proved  that  the  chemical 
action  of  an  acid  or  an  alkali  used  as  a  mouth  wash  for  neutralizing 
purposes  will  not  inhibit  dental  caries  to  any  great  degree.  All  of 
these  washes  are  supposed  to  contain  germicides  that  will  immediately 
destroy  the  micro5rganisms  of  the  mouth.  This  is  of  course  untrue, 
especially  when  the  short  time  they  are  retained  in  the  mouth  for  this 
purpose  is  considered.  The  peroxide  of  hydrogen  is  religiously  used 
by  many,  in  the  belief  that  the  oxygen  liberated  is  a  germicide  of 
sufficient  power  to  destroy  all  the  bacteria.  The  mechanical  action 
of  the  peroxide  in  its  boiling  process,  while  it  does  liberate  the  oxygen, 
is  more  effective  in  dislodging  particles  of  food  debris  around  the 
necks  of  the  teeth  than  in  its  germicidal  action  on  the  organisms  in 
the  mouth.  In  the  study  of  dental  caries  it  must  be  concluded  from 
the  present  knowledge  of  the  subject  that  in  the  main  Professor 
Miller's  theory  still  holds  good,  namely,  that  the  exciting  cause  is  due 
to  the  production  of  lactic  acid  by  the  action  of  microorganisms  on 
carbohydrates,  and  that  decay  takes  place  most  readily  on  those  sur- 
faces least  exposed  to  friction  during  mastication,  such  as  the  fissures 
or  pits,  approximal  surfaces,  and  the  necks  of  the  teeth.    Dr.  J.  Leon 


BRUSHING  359 

Williams  was  the  first  to  point  out  the  fact  that  a  thin  gelatinous 
placque  was  first  formed  on  the  surface  of  the  enamel  and  under  and 
in  this  thin  film  the  bacteria  obtained  a  secure  position  that  made 
their  dislodgement  difficult.  Their  action  in  the  production  of  acid  was 
intensified  when  thus  protected.  Other  scientific  investigators  have 
corroborated  Williams'  observations.  The  mucin,  which  is  a  product 
of  the  salivary  and  mucous  glands,  plays  an  important  part  in  the 
formation  of  these  placques.  Laying  aside  any  theories  regarding 
susceptibility  and  immunity,  it  must  be  admitted  that  the  battle  just 
now  should  be  the  thorough  removal  of  all  food  debris  and  the 
removal  of  these  placques  and  glue-like  accretions. 

At  the  present  time  there  is  considerable  agitation  in  dental  circles 
regarding  the  use  of  fruit  acids  to  prevent  dental  caries.  Mucin  is 
precipitated  from  the  secretions  in  the  mouth  by  the  presence  of  an 
acid.  This  precipitate  forms  on  the  surfaces  of  the  teeth  and 
becomes  the  factor  in  incasing  the  bacteria  with  food  debris  and  in 
forming  the  so-called  placques.  Mucin  thus  precipitated  is  soluble 
in  or  may  be  dissolved  by  an  alkali.  It  has  been  found  that  the  pres- 
ence of  fruit  acids  in  the  mouth  excites  a  flow  of  saliva  which  possesses 
quite  a  strong  alkaline  reaction.  It  is  claimed  by  these  investigators 
that  the  increased  alkalinity  of  the  saliva  has  a  solvent  action  on  the 
precipitated  mucin  and  a  neutralizing  action  on  lactic  acid  and  thus 
becomes  a  natural  preventive  of  dental  caries.  Other  investigators 
have  as  yet  been  unable  to  find  that  the  alkalinity  so  produced  is  of 
sufficient  strength  to  have  this  solvent  action.  Again,  it  is  claimed  that 
the  acids  of  fruits  have  a  curdling  effect  on  the  mucin,  forming  it  into 
flakes  which  are  easily  removed  from  the  tooth  surfaces. 

There  is  a  serious  question  concerning  the  habitual  use  of  these 
acids  for  this  purpose.  Practically  all  of  the  acids  of  fruits,  especially 
those  of  oranges  and  lemons,  if  used  too  freely  will  in  time  act  as  sol- 
vents for  the  cementing  substances  between  the  enamel  rods.  If  the 
deductions  of  these  investigators  were  entirely  correct  the  inhabitants 
of  the  tropics  would  be  found  to  be  quite  free  from  dental  caries,  which 
of  course  is  not  the  case.  Williams  has  observed  that  the  peasants 
working  in  the  orange  and  lemon  groves  of  Sicily  were  quite  immune 
to  caries,  and  Pickerill  also  cites  the  natives  of  New  Zealand  as  an 
example.  The  Italians  and  the  Sicilians  are  very  fond  of  hard  bread 
and  coarse  food,  and  if  a  scientific  investigation  were  made  regarding 
their  immunity  to  caries  other  powerful  factors  would  be  found  besides 
the  fruit  acids.  Those  who  live  in  the  orange  groves  of  Florida  are  far 
from  being  immune,  in  fact  the  reverse  is  the  rule.  The  American 
Indian,  who  did  not  eat  much  fruit,  enjoyed  a  considerable  immunity 
from  caries.  In  fact,  if  every  one  lived  an  out-of-door  life,  eating  coarse 
food  and  less  sugar,  there  would  be  but  little  need  of  the  dentist. 
A  reasonable  amount  of  fruit  is  healthful  and  desirable,  but  denti- 
frices and  mouth  washes  containing  fruit  acids,  must  be  used  with 
considerable  judgment. 


360  DENTAL  PROPHYLAXIS 

If  it  can  be  scientifically  shown  that  dentifrices  and  mouth  washes 
containing  fruit  acids  in  certain  proportions  are  harmless  to  the  teeth 
and  the  tissues  of  the  mouth  and  are  superior  to  any  of  the  present-day 
preparations  as  prophylactic  agents  for  dental  caries,  it  would  prove 
to  be  a  valuable  contribution  to  dental  prophylaxis. 

As  it  will  take  a  number  of  years  to  demonstrate  this  as  a  fact  it  will 
be  necessary  for  the  present  to  adhere  to  those  agents  that  have  proven 
themselves  to  be  harmless  and  efficient  in  the  past. 

The  most  cleansing  and  the  least  harmful  of  all  fruits  is  the  apple. 
This  with  its  dense  texture  acts  as  a  mechanical  cleanser,  and  the  malic 
acid  is  comparatively  harmless.  Where  it  is  impossible  to  have 
access  to  a  tooth-brush  the  eating  of  an  apple  will  be  found  an  excel- 
lent substitute. 

There  is  a  solvent  for  the  placques  and  accretions  on  the  surfaces  of 
the  teeth  that  is  quite  positive  in  its  action.  This  solvent  is  lime-water, 
and  is  made  from  the  coarse  calcium  oxid  or  unslaked  lime.  Its 
preparation  is  simple  and  cheap,  and  when  its  efficiency  for  the  use 
and  purpose  intended  is  considered,  it  will  rank  as  an  important  agent 
for  the  prevention  of  dental  caries. 

Some  coarse  lime,  such  as  is  used  in  making  rough  plaster,  may  be 
secured  from  a  paint  store  or  from  a  mason.  The  refined  product 
found  in  the  drug-stores  apparently  does  not  have  the  same  effect. 
The  refining  process  robs  it  of  some  of  its  beneficial  properties. 
It  is  cream  white  in  color.  The  lumps  should  be  broken  up  into 
coarse  powder  and  a  half-cupful  put  into  a  quart  bottle.  The  bottle 
should  be  nearly  filled  with  cold  water,  room  enough  being  left  to  per- 
mit of  thorough  shaking,  shaken  vigorously  and  set  aside  for  three 
or  four  hours  to  allow  the  lime  to  settle.  Then  as  much  of  the  clear 
water  as  possible  should  be  poured  off,  for  this  contains  the  washings 
of  the  lime.  It  will  be  found  impossible  to  pour  off  all  the  water 
without  losing  some  of  the  lime,  but  by  pouring  slowly  nearly  two- 
thirds  may  be  drawn  off.  The  bottle  can  then  be  filled  with  cold  water 
and  shaken  thoroughly,  when,  after  it  has  settled  again,  it  will  be 
ready  for  use.  A  bottle  of  convenient  size  should  be  procured;  one 
holding  ten  or  twelve  ounces,  and  filled  with  the  clear  water  from  the 
large  bottle.  This  smaller  bottle  will  be  more  convenient  to  use  at 
the  bowl.  The  large  bottle  can  be  again  filled  with  cold  water,  shaken 
thoroughly  and  set  aside  to  be  used  as  needed  (Fig.  195).  This 
operation  may  be  repeated  over  and  over  again,  for  the  original  half- 
cupful  of  lime  will  make  five  or  six  quarts  of  lime-water.  If  the  first 
use  of  the  w^sh  proves  that  it  is  a  little  strong,  it  can  be  diluted  in  the 
small  bottle.  With  new  patients  and  those  having  tender  gums  it  may 
have  to  be  diluted,  but  as  soon  as  ])()ssil)le  it  should  be  used  undiluted. 
When  taken  into  the  mouth  it  should  be  forced  IrM-k  and  forth  vigor- 
ously between  the  teeth  with  the  tongue  and  checks  and  the  rinsing 
contirmed  until  it  })reaks  into  a  foam.  Not  that  there  is  any  particu- 
larly beneficent  action  to  the  foaming,  but  if  it  is  worked  through  the 


BRUSHING 


361 


teeth  long  enough  to  make  the  foam  it  will  have  been  in  contact  with 
the  surfaces  of  the  teeth  long  enough  to  have  a  solvent  action  on  the 
placques  and  accretions.  Afterward  the  mouth  should  be  thoroughly 
rinsed  with  warm  water  to  take  away  the  taste  of  the  lime-water. 
It  is  the  unpleasant  taste  of  the  lime  that  makes  it  difficult  to  induce 
the  patients  to  use  it  at  the  start,  but  after  a  short  time  the  cleansing 
effect  is  so  pleasing  that  they  soon  forget  about  the  taste.  It  may  be 
flavored  with  saccharin  or  any  flavoring  material,  but  this  will  hardly 
be  found  necessary.  The  lime-water  should  be  used  after  the  brushing 
and  flossing,  after  each  meal. 


Fig.  195 


Summary  of  Prophylaxis. — One  prophylactic  treatment  does  not  con- 
stitute prophylaxis.  It  is  only  by  a  systematic,  continuous  course  of 
treatment  and  home  care  of  the  mouth  that  these  ideal  conditions  can 
be  secured.  It  is  estimated  that  all  great  educational  movements 
that  possess  real  merit  take  thirty  years  for  their  final  acceptance  and 
adoption.  Mouth  hygiene  has  been  agitated  for  fifteen  years.  The 
next  fifteen  years  will  see  its  rapid  spread  throughout  the  country  and 
its  practise  quite  general. 

Preventive  dentistry  can  be  had  quite  cheaply  and  is  within  the 
reach,  financially,  of  nearly  everybody.  Good  operative  dentistry 
is  expensive  and  always  will  be,  as  is  surgery  or  the  services  of  any 
educated  and  skilled  specialist. 

Prophylaxis  is  the  only  hope  of  solving  the  dental  problems  for  the 
masses  and  as  time  goes  on  it  will  be  found  as  necessary  a  form  of  insur- 
ance for  health  as  life  insurance  is  for  the  protection  of  those  left  after 
one  dies. 

When  the  public  really  becomes  educated  to  the  fact  that  for  the 


362  DENTAL  PROPHYLAXIS 

expenditure  of  a  very  moderate  sum  of  money  and  a  little  energy  on 
their  part,  they  may  retain  their  teeth  throughout  life  quite  free  from 
pain  and  disease,  there  will  be  a  great  demand  for  this  form  of  service. 
Every  mouth  would  be  greatly  benefited  if  these  treatments  could  be 
admuiistered  e\ery  two  months.  Many  mouths  require  monthly 
treatments,  especially  those  of  children  and  adults  who  are  susceptible 
to  caries. 

In  an  analysis  of  susceptibility  it  will  be  found,  in  many  cases, 
that  the  individual  is  indulging  in  too  much  candy  and  free  sugars. 
Children  are  given  crackers  or  cookies  just  before  going  to  bed,  and 
not  infrequently  in  bed,  to  keep  them  quiet.  Women  and  children 
especially  are  fond  of  sweets,  and  it  is  the  promiscuous  eating  of  them 
between  meals  that  creates  such  havoc  with  the  teeth. 

England,  France  and  America  are  consuming  too  much  sugar.  An 
educational  campaign  to  check  this  large  consumption  would  be  of 
great  help  in  our  problem.  Statistics  show  that  the  countries  where 
the  greatest  amount  of  sugar  is  eaten  are  the  countries  where  the  worst 
conditions  of  teeth  are  found.  The  sugar  consumption  per  capita 
has  increased  amazingly  during  the  past  forty  years  and  so  has  dental 
caries.  If  dentistry,  as  a  science,  had  not  advanced  so  rapidly  during 
this  same  period,  ruined  mouths  would  be  even  more  prevalent. 

In  the  search  for  some  easy  solution  of  the  problem  of  dental  decay 
many  ideas  are  advanced  for  its  ultimate  control,  and  it  is  expected 
that  a  simple  method  of  doing  away  with  this  great  disease-producing 
disorder  will  be  found.  There  may  come  a  time  when  a  lozenge  will 
produce  immunity  but  that  time  is  not  in  sight  as  yet.  As  long  as 
people  live  artificially,  as  most  people  do,  eating  the  various  concoc- 
tions called  "food"  that  they  feel  free  to  eat  at  the  present  time,  the 
one  hope  of  escape  from  the  ill-effects  of  dental  decay  and  its  attending 
serious  efl'ects  on  the  body  is  through  the  present  knowledge  of  extreme 
cleanliness,  or  mouth  hygiene.  Until  something  can  be  presented  more 
definitely  shnple  that  will  show  equally  beneficial  results,  it  will  be 
necessary  to  adhere  to  the  form  of  prophylaxis  herein  advocated. 

SOME  OFFICE  FACTS  AND  STATISTICS. 

In  the  writer's  practice  many  cases  of  interest  have  been  observed; 
individual  cases,  however,  always  lack  force,  for  there  may  be  a  ques- 
tion of  doubt  about  them,  but  a  demonstration  made  by  thirty  or  forty 
people  simultaneously  permits  of  comparisons  and  brings  conviction  to 
even  doubting  minds. 

This  enthusiasm  in  oral  prophylaxis  is  due  to  the  ideal  health  con- 
ditions obtained  in  the  mouths  of  patients,  to  their  consequent  physi- 
cal betterment  and  to  their  hearty  endorsement. 

In  the  early  part  of  the  year  1914  the  following  letter  was  sent  to 
two  hundred  of  the  writer's  patients: 


SOME  OFFICE  FACTS  AND  STATISTICS  363 

Bridgeport,  Conn.,  January,  1914. 


My  dear , 

In  preparing  some  lectures  on  the  subject  of  prophylaxis,  I  have 
found  it  desirable  to  offer  some  facts  and  statistics  concerning  my  own 
practice,  and  would  consider  it  a  personal  favor  if  you  would  kindly 
fill  out  the  enclosed  card  and  return  it  to  me. 

It  is  not  my  intention  to  use  any  names  or  any  individual  cards. 
I  merely  wish  to  get  at  the  truth  to  verify  statements  I  have  felt  war- 
ranted in  making  concerning  the  comparative  immunity  from  sickness 
when  the  mouth  is  kept  in  a  clean  and  wholesome  manner. 

We  know  that  many  of  the  infectious  diseases  of  childhood  emanate 
from  unsanitary  mouths,  these  with  their  decayed  teeth  and  decom- 
posing food  debris  being  ideal  incubators  for  germ  life.  We  know,  too, 
that  in  adults  whose  mouths  are  unclean  and  diseased,  the  intestinal 
tract  as  well  as  the  whole  nutritive  system  is  seriously  disturbed  and 
organic  infections  are  frequently  produced.  A  clean,  sanitary  mouth 
is  not,  of  course,  a  panacea  for  all  of  our  ailments,  but  we  know  that 
it  is  a  powerful  factor  for  good  health. 

It  is  a  fact,  frequently  mentioned  at  my  office,  that  it  is  extremely 
rare  for  a  patient  to  cancel  an  appointment  on  account  of  illness,  and 
I  feel  it  would  be  helpful  to  the  dental  profession  in  advancing  this 
work  of  prevention  if  additional  facts  of  this  nature  could  be  secured. 

I  realize  that  it  is  something  of  an  imposition  and  rather  an  unpre- 
cedented thing  to  do,  but  feel  that  the  cause  involved  is  sufficiently 
great  to  warrant  my  asking  this  favor. 

If  for  any  reason  you  would  rather  not  fill  out  the  card  please  feel 
free  to  ignore  it. 

Yours  very  sincerely, 

Alfred  C.  Fones. 

With  this  letter  w^as  enclosed  a  card  on  which  were  printed. the 
following  questions: 

Name 

Have  you  been  ill  duiing  1913? , 

If  so,  was  the  illness  of  long  duration? 

If  you  do  not  object  will  you  state  illness? •.  .  . 

Do  you  feel  that  mouth  hygiene  has  benefited  you  physically? 

Any  remarks 

Signed 

The  object  in  sending  these  letters  and  cards  was  to  secure  some  data 
relative  to  the  physical  influence  of  mouth  hygiene  upon  the  every- 
day life  of  both  children  and  adults  and  also  to  get  an  expression  of 
opinion  as  to  whether  or  not  mouth  hygiene,  as  a  factor  for  good  health, 
was  appreciated  by  the  patients.  Perhaps  the  last  question  was  not 
very  fortunately  worded.  It  w^as  not  expected  that  the  patients  would 
experience  any  pronounced  glow  of  health  coming  over  them  after 
following  the  system  of  mouth  cleanliness  for  a  period  of  time;  still  in 


364  DENTAL  PROPHYLAXIS 

spite  of  this  perplexing  question  the  answers  were  both  interesting  and 
quite  satisfactory,  as  the  tables  will  show.  At  the  time  it  became  neces- 
sary to  use  this  data,  one  hundred  and  sixty  cards  had  been  returned, 
or  80  per  cent,  of  those  sent  out. 

A  study  of  the  following  tables  of  the  answers  returned  will  at  least 
prove  interesting,  even  if  no  scientific  data  are  found. 

To  the  question,  "Have  you  been  ill  during  1913?"  the  cards  showed 
the  following  answers: 
14  stated  illness. 
11  had  colds  (now  and  then). 
135  had  no  illness. 
These  figures  show  that  85  per  cent,  of  these  patients  had  been  free 
from  all  sickness. 
Of  the  fourteen  who  had  been  ill  the  following  table  gives  details: 


Duration  of 

Illness. 

SFumber. 

illness. 

Child. 

Adult 

Grippe  .... 

2 

3  days  each 

1 

1 

Tonsillitis    . 

2 

4  days — 2  weeks 

2 

Nervous  trouble     . 

1 

"Not  long" 

1 

Whooping-cough    . 

1 

"Quite  long" 

1 

Acute  indigestion  . 

1 

2  days 

1 

Appendicitis      . 

2 

4  weeks — "not  long" 

2 

Pleurisy 

2 

1  week — ^"not  long" 

1 

1 

Sore  throat 

2 

5  days — "not  long" 

2 

Bronchitis  . 

1 

"A  few  days" 

1 

Although  a  diseased  or  unsanitary  mouth  would  be  capable  of 
producing  most  of  the  ailments  noted  in  this  list,  it  must  be  remem- 
bered that  these  patients  present  healthy  mouths  and  are  reasonably 
faithful  in  their  care. 

Under  such  conditions  it  would  seem  justifiable  to  eliminate  the 
following  from  the  table: 

Two  cases  of  appendicitis,  the  operation  for  one  of  which  had  been 
previously  planned  for  two  months  and  the  other  one  being  a  recur- 
rent attack  soon  controlled  and  not  requiring  an  operation,  one  of 
acute  indigestion,  one  nervous  trouble,  and  two  of  pleurisy. 

This  list,  under  the  above  conditions,  would  not  be  susceptible  to 
serious  debate  as  being  caused  through  mouth  infection.  The  remain- 
ing ailments  partially  prove  that  mouth  hygiene  does  not  secure  abso- 
lute immunity  to  infectious  diseases,  yet  it  must  be  conceded  that 
the  length  of  illness,  with  the  exception  of  the  two  weeks  of  tonsillitis, 
is  sur[)risingly  short.  If  the  eleven  who  stated  "colds  now  and  then" 
are  eliminated  and  charged  up  to  overfeeding,  there  are,  as  a  last 
analysis,  eight  people  out  of  one  hundred  and  sixty  who  were  ill  during 
1913  with  forms  of  illness  from  which  to  the  writer's  minil,  mouth 
hygiene  sliould  liaxc  made  them  immune.  To  try  to  claim  everything 
in  sight  would  be  discourteous  to  the  medical  profession,  but  in  a 
broad  sense  it  may  be  stated  that,  omitting  the  list  of  colds,  over  90 
per  cent,  were  free  from  sickness  and  ninety-five  were  free  from  infec- 
tions di.seases. 


A  SYSTEM  FOR  PIIOPIIYLAXIS  IN  DENTAL  PRACTICE       365 

Considerable  interest  may  be  found  in  the  answers  to  the  last 
question  which  was: 

"Do  you  feel  that  mouth  hygiene  has  benefited  you  physically?" 
53  answered  "Yes." 
10  answered  "Cannot  say." 
3  space  blank,  no  comment. 
37  stated  an  appreciation  of  prophylaxis. 
51  specific  statements  of  physical  betternu>nt. 

This  question  was  inspired  by  the  comment  of  numerous  dentists 
who  had  stated  that  patients  would  have  but  little  appreciation  of 
prophylaxis.  If  the  question  had  been  instead,  "Do  you  feel  that 
mouth  hygiene  is  a  physical  benefit?"  it  would  have  shown  whether 
or  not  the  patients  had  an  understanding  of  its  importance  and  would 
in  itself  have  answered  the  comments. 

Considering  the  blunt  way  the  question  appeared  on  the  card,  the 
answers  were  highly  satisfactory,  and  although  they  give  no  scientific 
data,  they  surely  indicate  a  reasonable  degree  of  enthusiasm  for  the 
science  of  prophylaxis.  Twenty-seven  stated  their  appreciation 
without  comments  of  physical  betterment.  Fifty-one  stated,  in  a 
general  way,  that  they  felt  mouth  hygiene  had  benefited  their  general 
health  and  six  named  the  disappearance  of  their  ailments.  Of  the 
latter  two  had  recovered  from  chronic  indigestion,  one  noted  the  dis- 
appearance of  headaches,  and  three  stated  the  disappearance  of  throat 
irritation. 

It  must  be  remembered  that  these  cards  form  a  record  of  but  one 
hundred  and  sixty  people  of  all  ages  for  but  one  year.  Whether  an 
additional  one  hundred  and  sixty  cards  would  add  to  the  interest  of 
these  tables  is  hard  to  determine  without  trying  it  out.  Scientific 
facts  cannot  be  based  on  any  general  investigation  of  this  kind,  but  it 
must  be  admitted  that  the  evidence  submitted  is  at  least  favorable 
to  mouth  hygiene. 

A  SYSTEM  FOR  PROPHYLAXIS  IN  DENTAL  PRACTICE. 

First  a  new  patient  is  given  two  appointments,  a  week  or  ten  days 
apart,  with  the  dental  hygienist,  for  a  thorough  instrumentation  and 
polishing  of  the  teeth. 

At  the  end  of  the  first  sitting  he  is  supplied  with  a  tooth-brush, 
dentifrice,  floss  silk  and  lime-water  for  a  mouth  wash,  taken  to  a  wash 
bowl  and  taught  how  to  properly  brush  teeth  and  gums,  and  given 
full  instructions  in  the  home  care  of  the  mouth. 

At  the  end  of  the  second  sitting  one-half  hour  is  reserved  for  him 
with  the  dentist  for  a  thorough  chart  examination.  Appointments 
are  then  arranged  and  the  teeth  restored  to  a  sound  condition.  At 
the  end  of  the  last  appointment  the  dentist  gives  the  patient  a  thorough 
prophylactic  treatment. 

The  patient  is  then  put  on  a  list  and  sent  for  each  month  for  a 


366  DENTAL  PROPHYLAXIS 

treatment  by  the  dental  hygienist.  At  the  end  of  six  months  he 
again  goes  into  the  hands  of  the  dentist  for  a  thorough  prophylactic 
treatment  and  examination  of  the  teeth  and  gums  and  if  the  condition 
of  his  mouth  warrants,  the  interval  between  the  treatments  is  now 
lengthened  to  six  weeks.  At  the  end  of  the  next  six  months  he  again 
goes  through  the  dentist's  hands  and  if  good  mouth  health  is  attained 
his  name  is  placed  on  a  two  months'  list  and  he  is  given  treatments 
by  the  dental  hygienist  at  these  intervals,  going  into  the  dentist's 
hands  for  every  third  treatment,  or  once  in  six  months.  Patients 
whose  mouths  are  very  susceptible  to  dental  caries,  such  as  children 
and  young  people,  should  be  retained  on  the  monthly  or  six  weeks' 
list. 

When  the  patient's  mouth  has  been  put  in  order  and  his  name  placed 
on  one  of  the  lists  to  be  sent  for  at  regular  intervals,  his  name  is  also 
entered  in  the  appointment  book  against  the  date  when  his  next 
appointment  for  a  prophylactic  treatment  falls  due.  A  week  previous 
to  this  date  the  patient  is  notified  of  the  appointment  by  means  of 
a  return  card  system.  This  consists  of  an  appointment  card  bearing 
the  name  of  the  patient  and  date  and  hour  of  his  appointment,  a  return 
card  bearing  the  same  date,  and  a  stamped  return  envelope.  If  the 
date  designated  proves  convenient,  the  patient  signs  the  return  card 
and  returns  it  in  the  enclosed  envelope  and  the  appointment  is  checked 
in  the  appointment  book.  If  not  convenient,  a  new  appointment  is 
made.  The  various  lists  of  patients — monthly,  six  weeks  and  two 
months — are  kept  by  means  of  a  card-index  file. 


CHAPTER  XIII. 
CHEMISTRY  OF  FOOD  AND  NUTRITION. 

By  RUSSELL   H.  CHITTENDEN,  Ph.D.,  LL.D.  Sc.D. 

Part  I. 

In  a  popular  sense,  under  the  term  food  is  included  all  those  sub- 
stances which  man,  following  the  dictates  of  a  capricious  appetite, 
is  in  the  habit  of  eating.  In  this  sense,  food  comprises  a  large  number 
of  substances  or  products  belonging  to  the  animal  and  the  vegetable 
kingdoms.  If,  however,  we  attempt  a  chemical  analysis  of  the  various 
foods  which  man  is  accustomed  to  eat,  it  is  found  that  they  contain 
one  or  more  of  six  distinct  classes  or  principles.  These  are  known  as 
proteins,  albuminoids,  fats,  carbohydrates,  inorganic  salts  or  mineral 
matter,  and  water. 

In  a  physiological  sense,  a  food  is  a  substance  which  helps  maintain 
the  integrity  of  the  body  tissues,  thus  insuring  a  normal  condition  of 
the  body  protoplasm.  This  implies  not  merely  the  integrity  of  the 
tissues  of  the  body  as  a  whole,  but  likewise  the  integrity  of  each  indi- 
vidual unit  of  the  tissues,  i.  e.,  the  tissue  cells.  Food  must  supply 
material  for  the  growth  of  new  tissue  as  in  the  young,  and  for  the 
repair  or  maintenance  of  wasting  tissues  in  the  adult. 

Further,  a  food,  in  the  strict  physiological  sense,  must  not  only 
contribute  to  the  maintenance  of  the  tissues,  but  it  must  likewise  fur- 
nish energy  to  meet  the  daily  needs  of  the  body;  energy  which  will 
manifest  itself  in  the  form  of  heat  or  work,  as  the  case  may  be.  It 
should  also  help  maintain  and  strengthen  the  defenses  of  the  body 
against  disease,  or  disease  germs.  In  other  words,  physiologically 
speaking,  a  food  must  help  keep  up  the  normal  nutritional  rhythm 
of  the  body.  Again,  a  food,  if  it  conforms  to  the  physiological  defini- 
tion, must  not  be  in  any  sense  inimical,  or  harmful,  to  any  of  the  tis- 
sues or  any  of  the  processes  of  the  body. 

Of  the  various  food  principles,  the  proteins  taken  as  a  class  are, 
for  many  reasons,  the  most  important.  They  are  composed  of  carbon, 
hydrogen,  nitrogen,  oxygen,  sulphur,  and  some  contain  phosphorus. 
As  a  rule  they  contain  approximately  52  per  cent,  of  carbon,  7  per 
cent,  of  hydrogen,  16  per  cent,  of  nitrogen,  22  per  cent,  of  oxygen, 
0.5  to  2  per  cent,  of  sulphur,  the  phosphorus  when  present  being  con- 
tained ordinarily  in  small  amount.  Protein  foodstuffs  are  widely 
distributed  throughout  the  animal  and  vegetable  kingdoms,  and  while 
they  differ  somewhat  among  themselves,  both  in  chemical  composi- 
tion and  in  physiological  behavior,  they  are  alike  in  containing  approx- 
imately 16  per  cent,  of  nitrogen.    They  are  therefore  referred  to  as 


368  CHEMISTRY  OF  FOOD  AND  NUTRITION 

nitrogenous  foods.  Proteins,  furthermore,  are  likewise  spoken  of  as 
essential  foods,  because  they  are  absolutely  essential  for  life.  In  the 
definition  given  of  a  food,  it  was  stated  that  a  food  is  a  substance  which 
helps  maintain  the  integrity  or  normal  condition  of  the  tissues  of  the 
body,  which  means  as  well  the  condition  of  the  cell  protoplasm.  The 
functional  activity  of  a  tissue,  whatever  it  may  be,  depends  upon  the 
functional  activity  of  the  individual  elements  of  that  tissue,  i.  e.,  the 
tissue  cells,  and  the  chemical  basis  of  a  cell  is  the  cell  protoplasm. 
Again,  the  important  part  of  the  cell  protoplasm  is  the  ptotein  material 
which  it  contains.  Every  living  cell  of  the  body,  whatever  its  nature, 
whatever  its  origin,  whether  it  be  an  exceedingly  active  tissue  like 
the  muscle  tissue  or  brain  tissue,  or  whether  it  be  a  very  inactive 
tissue  like  bone  and  teeth,  is  made  up  of  cell  protoplasm,  and  the  cell 
protoplasm  in  every  case  is  composed  largely  of  protein  material. 
These  tissue  cells,  or  their  contained  protoplasm,  are  not  able  to  renew 
the  waste  of  cell  substances  except  through  the  intake  of  protein  food. 
Growing  tissues  likewise  are  dependent  upon  the  intake  of  fresh  pro- 
tein material  to  accomplish  growth.  The  nitrogenous  or  protein  foods 
are  therefore  essential  foods,  necessary  for  maintenance  and  for  growth. 
In  no  other  way  than  by  the  intake  of  protein  food  can  the  protein 
material  of  cell  protoplasm  be  renewed. 

As  has  been  stated,  phosphorus  is  not  common  to  all  proteins;  but 
there  is  a  certain  group  of  very  important  proteins  practically  present 
in  all  tissue  cells,  and  consequently  playing  a  very  important  part  in 
nutrition,  substances  which  contain  phosphorus  in  quite  appreciable 
amounts.  These  phosphorized  proteins  are  generally  termed  nucleo- 
proteins,  since  they  are  composed  of  a  peculiar  phosphorized  substance 
known  as  nuclein  or  nucleic  acid  combined  with  protein. 

Albuminoids  are  substances  closely  related  to  the  proteins,  contain- 
ing nitrogen  in  essentially  the  same  amount  as  a  true  protein  in  addition 
to  carbon,  hydrogen,  oxygen  and  sulphur,  but  they  differ  from  the 
proteins  proper  in  that  they  have  a  different  nutritional  value.  Gelatin 
is  a  typical  albuminoid,  a  substance  which,  while  resembling  protein 
in  many  respects,  is  not  able  to  support  life  to  the  same  degree  that  a 
true  protein  can. 

As  distinguished  from  the  proteins,  fats  and  carbohydrates  are  fre- 
quently termed  non-nitrogenous  foods,  owing  to  the  fact  that  they 
contain  no  nitrogen,  but  are  composed  solely  of  carbon,  hydrogen, 
and  oxygen.  Carbohydrates  contain  approximately  40  per  cent,  of 
carbon,  while  the  hydrogen  and  oxygen  present  are  in  such  proportions 
as  to  form  a  certain  number  of  molecules  of  water;  hence  the  name 
carbohy<lrates.  Fats,  on  the  other  hand,  contain  far  more  carbon 
than  the  carbohydrates,  api)roximately  75  per  cent,  or  more,  and  on 
account  of  this  larger  projjortion  of  carbon  have  a  higher  calorific  value 
or  heat-producing  i)ower  than  carbohydrates  possess. 

The  inorganic  salts  or  mineral  matter,  which  are  present  in  practi- 
cally all  foodstuffs  in  greater  or  less  degree,  play  an  important  part 


CHEMISTRY  OF  FOOD  AND  NUTRITION 


369 


in  the  niitpition  of  the  body,  being  necessary  for  the  development  and 
growth  of  such  solid  tissues  as  bone  and  teeth.  Many  inorganic  salts 
play  a  part  likewise  in  influencing  certain  of  the  nutritional  processes. 
They  are  present  in  the  protoplasm  of  all  tissues  and  are  essential,  as  is 
also  water,  in  helping  to  maintain  the  normal  composition  of  the  body 
tissues.  Of  the  inorganic  salts  especially  conspicuous  are  phosphates, 
chlorides  and  sulphates  of  sodium,  potassium,  calcium,  magnesium, 
and  iron. 

THE  CHEMICAL  COMPOSITION  OF  SOME  COMMON  FOOD  MATERIALS.' 


Food  materials. 

Protein, 
per  cent. 

Carbo- 
hydrate, 
per  cent. 

Fat, 
per  cent. 

Water, 
per  cent. 

Mineral 
matter, 
per  cent. 

Fuel 

value  per 

pound, 

calories. 

Fresh  beef,  round,  lean,  edible 

part 

22.3 

0 

2.8 

73.6 

1.3 

540 

Fresh       porterhouse       steak, 

edible  part 

21.9 

0 

20.4 

60.0 

1.0 

1270 

Fresh  beef  liver       .... 

21.0 

1.7 

4.5 

71.2 

1.6 

605 

Fresh  beef  tongue  .... 

19.0 

0 

9.2 

70.8 

1.0 

740 

Fresh  sweetbreads  .... 

16.8 

0 

12.1 

70.9 

1.6 

825 

Cooked  beef,  roasted    . 

22.3 

0 

28.6 

48.2 

1.3 

1620 

Broiled  tenderloin  steak    . 

23.5 

0 

20.4 

54.8 

1.2 

1300 

Lamb  chops,  broiled     . 

21.7 

0 

29.9 

47.6 

1.3 

1665 

Chicken,  broilers,  edible  part 

21.5 

0 

2.5 

74.8 

1.1 

505 

Roast  turkey,  edible  part 

27.8 

0 

18.4 

52.0 

1.2 

1295 

Fricasseed  chicken,  edible  part 

17.6 

2.4 

11.5 

67.5 

1.0 

855 

Fresh  mackerel,  edible  part    . 

18.7 

0 

7.1 

73.4 

1.2 

645 

Fresh  halibut,  steaks    . 

18.6 

0 

5.2 

75.4 

1.0 

565 

Fresh  oysters,  solid 

6.0 

3.3 

1.3 

88.3 

1.1 

230 

Fresh  hen's  eggs      .... 

13.4 

0 

10.5 

73.7 

1.0 

720 

Butter 

1.0 

0 

85.0 

11.0 

3.0 

3605 

Full  cream  cheese   .... 

25.9 

2.4 

33.7 

34.2 

3.8 

1950 

Whole  cow's  milk   .... 

3.3 

5.0 

4.0 

87.0 

0.7 

325 

Oatmeal 

16.1 

67.5 

7.2 

7.3 

1.9 

1860 

Rice 

8.0 

79.0 

0.3 

12.3 

0.4 

1630 

Wheat  flour,  entire  wheat 

13.8 

71.9 

1.9 

11.4 

1.0 

1675 

Shredded  wheat      .... 

10.5 

77.9 

1.4 

8.1 

2.1 

1700 

Macaroni 

13.4 

74.1 

0.9 

10.3 

1.3 

1665 

Wheat  bread  or  rolls    . 

8.9 

56.7 

4.1- 

29.2 

1.1 

1395 

Soda  crackers 

9.8 

73.1 

9.1 

5.9 

2.1 

1925 

Fresh  asparagus      .... 

1.8 

3.3 

0.2 

94.0 

0.7 

105 

Dried  beans 

22.5 

59.6 

1.8 

12.6 

3.5 

1605 

Dried  peas 

24.6 

62.0 

1.0 

9.5 

2.9 

1655 

Green  peas 

7.7 

16.9 

0.5 

74.6 

1.0 

465 

Boiled  potatoes       .... 

2.5 

20.9 

0.1 

75.5 

1.0 

440 

Apples,  edible  part 

0.4 

14.2 

0.5 

84.6 

3.0 

290 

Bananas,  yellow,  edible  part  . 

1.3 

22.0 

0.6 

75.3 

0.8 

460 

Fresh  strawberries 

1.0 

7.4 

0.6 

90.4 

0.6 

180 

Almonds,  edible  part    . 

21.0 

17.3 

54.9 

4.8 

2.0 

3030 

Peanuts,  edible  part 

25.8 

24.4 

38.6 

9.2 

2.0 

2560 

Pine  nuts,  edible  part 

33.9 

6.9 

49.4 

6.4 

3.4 

2845 

By  chemical  analysis 

of  food 

materi 

als  one 

learns 

regard! 

ng  the 

proportion  of  protein,  carbohydrate,  fat,  etc.,  present  therein.     The 
preceding  table  gives  a  few  data  bearing  on  the  composition  of  some 

1  Bulletin  28,  U.  S.  Department  of  Agriculture,  Experiment  Station  Bulletin. 
24 


370  CHEMISTRY  OF  FOOD  AND  NUTRITION 

common  food  materials.  The  last  column  of  figures,  showing  fuel 
value  per  pound,  will  be  considered  later.  It  is  to  be  noted,  first,  that 
all  ordinary  food  products  contain  a  large  amount  of  water.  Water 
is  a  very  important  part  of  food,  just  as  it  is  an  important  part  of  the 
tissues  of  the  body.  Fresh  meats,  for  example,  contain  approximately 
70-75  per  cent,  of  water;  but  when  roasted  or  broiled  a  large  proportion 
of  this  water  is  evaporated.  Thus,  while  fresh  lean  beef  may  have 
73  per  cent,  of  water  in  it,  roasted  beef  may  contain  only  48  per  cent. 
Some  animal  foods,  such  as  oysters,  contain  a  relatively  small  amount 
of  solid  matter — 12  per  cent,  only,  as  seen  in  the  table.  Similarly,  among 
vegetable  foods,  such  articles  as  fresh  asparagus,  strawberries,  etc., 
are  likewise  poor  in  solid  matter;  6-10  per  cent.  The  more  important 
points  regarding  the  composition  of  foodstuffs  to  be  emphasized,  how- 
ever, are  (1)  that  foods  of  animal  origin  are,  as  a  rule,  rich  in  protein 
and  contain  little  or  no  carbohydrate;  (2)  that  foods  of  vegetable  origin 
are  ordinarily  very  rich  in  carbohydrate  matter,  some  containing  only 
a  comparatively  small  amount  of  protein,  while  others,  such  as  peas, 
beans,  nuts,  etc.,  may  contain  as  much  protein  as  ordinary  animal 
food.  In  milk,  after  eliminating  the  water,  all  three  of  the  organic 
food  principles  are  equally  conspicuous.  In  edible  nuts  also,  such  as 
almonds  and  peanuts,  protein,  carbohydrate  and  fat  are  all  three 
present  in  large  amounts;  fat  being  especially  abundant.  In  some  nuts, 
such  as  pine  nuts,  carbohydrate  may  be  present  in  a  relatively  small 
amount,  thus  constituting  a  food  rich  in  protein  and  fat,  but  poor  in 
carbohydrate. 

The  carbohydrates  of  our  food  supply  are  mainly  in  the  form  of 
starches,  abundant  in  cereals  and  other  vegetable  foodstuffs.  Sugars, 
gums,  etc.,  are  likewise  abundant  components  of  the  daily  food.  All 
carbohydrates  are  made  available  for  the  needs  of  the  body  by  diges- 
tion, and  are  eventually  absorbed  into  the  blood  as  simple  sugars, 
chiefly  dextrose,  but  in  some  measure  also  as  levulose  and  galactose. 
Carbohydrates  may  be  divided  into  three  groups;  polysaccharides, 
of  which  starch  is  a  type;  disaccharides,  such  as  cane  sugar,  milk 
sugar,  and  maltose,  and  monosaccharides,  such  as  dextrose,  levulose, 
and  galactose.  It  is  only  in  the  form  of  monosaccharides,  or  simple 
sugars,  that  carbohydrates  can  be  utilized  directly  by  the  body.  Conse- 
quently, it  is  the  purpose  of  digestion  through  the  enzymes  of  the  diges- 
tive juices  to  transform  the  polysaccharides,  such  as  starch,  and  the 
disaccharides,  such  as  cane  sugar,  into  the  monosaccharides  dextrose, 
galactose,  etc.  Eventually  the  carbohydrates  taken  into  the  body  as 
food  are  oxidized  in  the  tissues  to  carbon  dioxid  and  water.  The 
chief  value  of  carbohydrate  food  to  the  body  is  that  it  constitutes 
a  source  of  energy  for  the  needs  of  the  tissue  cells,  expecially  for  muscu- 
lar work,  and  as  a  supply  for  the  heat  needed  by  the  body.  A  gram  of 
sugar  yields  on  oxidation  four  calories  of  heat,  and  in  this  connection 
it  is  to  be  remembered  that  carbohydrates  form  the  largest  part  of 
the  daily  diet.    Further,  as  they  are  easily  oxidized  in  the  body,  they 


CHEMISTRY  OF  FOOD  AND  NUTRITION  371 

constitute,  therefore,  especially  available  material  for  maintaining 
the  supply  of  animal  heat.  At  the  same  time,  as  already  stated,  the 
body  can  utilize  directly  only  the  monosaccharides.  Cane  sufi;ar,  for 
example,  though  soluble  and  diffusible,  is  not  directly  available  for 
the  needs  of  the  body,  but  must  be  split  apart  by  an  appropriate  fer- 
ment or  invert  enzyme  into  the  two  molecules  of  a  monosaccharide. 

C12H22O11  +  H2O  =  CeHnOfi  +  CeHisOe 

Saccharose.  Water.  Dextrose.  Levulose. 

Similarly,  milk  sugar  must  undergo  inversion  into  the  monosacchar- 
ides dextrose  and  galactose,  as  a  preliminary  step  in  its  utilization  by 
the  body.  It  is  plain  from  the  chemical  composition  of  carbohydrates, 
lacking  as  they  do  nitrogen,  that  they  cannot  by  themselves  serve  to 
build  up  protoplasm.  Man  cannot  live  on  carbohydrate  food  alone, 
no  matter  how  abundantly  supplied.  He  would  eventually  starve  to 
death  owing  to  lack  of  protein  food;  but  as  we  shall  see  later  on,  the 
carbohydrates  serve  to  protect  protein  material  in  some  degree.  The 
energy  which  is  furnished  by  their  oxidation  helps  to  maintain  the 
supply  of  heat  and  enables  the  tissues  of  the  body  to  obtain  the  energy 
needed  for  their  special  kinds  of  work,  and  in  this  way  the  carbohydrate 
foods  protect  the  protein  of  the  tissues  of  the  body,  enabling  the  body 
to  maintain  a  good  nutritive  condition  on  a  reduced  amount  of  pro- 
tein food.  Lastly,  it  should  be  mentioned  that  carbohydrate  taken 
as  food  in  quantities  greater  than  is  needed  for  the  immediate  wants 
of  the  body  is  stored  up  in  the  form  of  glycogen  in  the  liver,  or  it  may 
be  transformed  into  fat  and  deposited  in  the  various  tissues  of  the 
body. 

The  fats  contained  in  the  daily  diet  by  their  oxidation  furnish  a 
part  of  the  heat  energy  needed  to  maintain  the  body  temperature; 
their  high  calorific  value  making  them  more  effective  in  this  respect 
than  carbohydrates.  Likewise  fats  are  stored  in  the  various  tissues 
of  the  body,  thus  constituting  a  reserve  which  can  be  drawn  upon 
in  case  of  deficiency  of  food  or  during  complete  fasting.  Like  carbo- 
hydrates, fat  also  protects  the  protein  of  the  tissue  from  consumption. 
On  the  other  hand,  fats  are  not  so  easily  digested  as  carbohydrates, 
and  hence  their  energy  value  is  not  so  readily  available  as  that  of 
carbohydrates. 

The  processes  of  nutrition,  or  the  chemical  changes  of  metabolism, 
are  essentially  exothermic,  i.  c,  they  are  attended  by  the  production 
of  heat.  The  term  "  metabolism"  includes  practically  all  those  changes 
that  occur  in  our  foodstuffs  from  the  time  they  are  absorbed  in  the 
alimentary  canal  until  they  are  cast  out  of  the  body  in  the  various 
excretions.  The  digested  food  material  absorbed  from  the  gastro- 
intestinal tract  by  the  blood  is  carried  to  the  tissues,  and  is  there,  in 
part  at  least,  transformed  into  the  living  protoplasm  of  the  cell.  This 
building  up  of  cell  protoplasm  from  the  food  material  is  an  anabolic 
process.    The  breaking  down  of  .the  material  of  the  tissue  cells  is,  on 


372  CHEMISTRY  OF  FOOD  AND  NUTRITION 

the  other  hand,  a  catabolic  process.  The  breaking  down  of  the  complex 
molecules,  either  of  food  material  or  of  the  tissues,  is  primarily  the 
result  of  oxidation.  These  processes  of  oxidation  may  be  slow  or  they 
may  be  rapid,  but  in  any  case  the  ultimate  products  are  essentially 
the  same.  The  carbon  of  the  protein  molecule,  the  carbon  of  the  fat, 
or  the  carbon  of  the  carbohydrate,  is  eventually  oxidized  to  carbon 
dioxid. 

Similarly,  hydrogen  and  sulphur  of  the  protein  molecule  are  oxidized 
to  water  and  sulphur  dioxid;  the  latter  eventually  appearing  in  the 
excretion  as  a  salt  of  sulphuric  acid.  In  the  case  of  nucleoproteins, 
the  phosphorus  is  oxidized  somewhere  in  the  body  with  the  formation 
of  phosphoric  acid,  which  eventually  combines  with  an  alkali  or  with 
an  alkali  earth,  and  thus  there  results,  for  example,  sodium  phosphate 
or  it  may  be  calcium  phosphate.  As  calcium  phosphate  it  may  be 
deposited  in  the  teeth  or  in  the  bones,  making  a  noticeable  part  of 
these  solid  tissues. 

As  has  been  stated,  the  processes  of  oxidation,  the  processes  of 
metabolism,  as  they  occur  in  the  body,  are  usually  slow.  Whereas, 
protein,  fat  or  carbohydrate  oxidized  outside  of  the  body  are  broken 
do^Ti  at  once  into  the  ultimate  simple  products,  such  as  carbon  dioxid, 
water,  etc.,  in  the  body  the  steps  are  quite  different.  Sir  Michael 
Foster  once  said  that  the  processes  of  metabolism,  so  far  as  we  can 
measure  them,  may  be  compared  to  a  flight  of  stairs.  The  complex 
protein  molecule,  for  example,  taken  into  the  body  as  food  and  even- 
tually made  a  component  part  of  the  tissues,  starts  on  its  catabolic 
changes,  breaking  do-^Ti  step  by  step  into  simpler  compounds,  until 
at  last  the  final  end-products,  carbon  dioxid,  water,  sulphur  dioxid, 
urea,  etc.,  are  formed.  Each  step  in  the  process  corresponds  to  a  step 
in  the  flight  of  stairs.  As  a  rule,  then,  we  see  that  the  metabolic  pro- 
cesses are  gradual,  step  by  step.  Sugar,  for  example,  or  carbohydrate 
food  in  general,  is  probably  broken  down  and  oxidized  by  the  succes- 
sive action  of  a  series  of  enzymes  or  digestive  ferments,  with  the  pro- 
duction of  a  number  of  intermediate  products,  each  product  being 
simpler  than  the  preceding  one.  Thus,  we  have  what  we  call  inter- 
mediary metabolism,  meaning  a  series  of  gradual,  progressive  decom- 
positions. In  some  cases  it  is  possible  to  trace  out  these  processes 
step  by  step,  from  organ  to  organ,  or  from  tissue  to  tissue,  and  we  find 
a  row  of  bodies  intermediary  between  protein  and  urea,  for  example, 
each  one  of  the  substances  so  formed  corresponding  to  Sir  Michael 
Foster's  steps  in  this  flight  of  stairs,  until  the  bottom  step  is  reached. 
The  ultimate  result,  so  far  as  heat,  for  example,  is  concerned,  is  essen- 
tially the  same  whether  the  oxidation  is  what  we  might  call  an  explosive 
decomposition  with  direct  formation  of  tlie  ultimate  products,  or 
whether  it  is  a  slow  or  gradual  process,  with  liberation  of  heat  at  each 
step  in  the  breaking  down  of  the  materials.  In  many  of  these  inter- 
mediary steps,  transformations  are  so  slight  that  the  amount  of  heat 
resulting  is  very  small.     If  we  take,  for  example,  the  disaccharide 


CHEMISTRY  OF  FOOD  AND  NUTRITION  373 

maltose  (C12H22O11)  which  by  hydrolysis  is  broken  down  into  two  molec- 
ules of  the  monosaccharide  dextrose  (C6H12O6),  we  find  in  this  process 
of  hydrolysis  that  only  about  3.3  calories  result.  If,  however,  dextrose 
is  burned  up  in  the  tissues  of  the  body  at  one  step,  or  in  the  laboratory, 
to  its  ultimate  products,  carbon  dioxid  and  water,  we  have  a  relatively 
large  amount  of  heat  produced.  The  point  to  be  emphasized  is,  that 
in  all  these  chemical  processes  occurring  in  the  body  heat  is  liberated, 
and,  as  already  stated,  they  are  in  the  main  oxidations  which  are 
effected  through  the  influence  of  oxidizing  enzymes  or  some  other 
kindred  means  of  activating  oxygen. 

The  great  supply  of  heat  energy  needed  by  the  living  body  to  main- 
tain its  normal  temperature  comes  from  these  oxidative  processes. 
The  heat  produced  in  the  body  is  expressed  as  calories.  The  small 
calorie,  or  gram  degree  unit  of  heat,  may  be  defined  as  the  quantity  of 
heat  necessary  to  raise  one  gram  of  water  one  degree  centigrade  in 
temperature,  while  the  large  calorie,  or  kilogram  calorie,  is  the 
quantity  of  heat  necessary  to  raise  the  temperature  of  one  kilogram 
of  water  one  degree.  In  other  words,  the  large  calorie  is  one  thou- 
sand times  larger  than  the  small  calorie.  It  is  generally  stated  that 
a  man  of  average  body  weight  and  activity  produces  and  gives  off 
about  2,500,000  small  calories  of  heat  per  day.  This  would  mean 
2500  large  calories  of  heat.  This  heat  comes  obviously  from  the 
physiological  oxidation  of  the  food  materials  taken  into  the  body, 
namely,  the  proteins,  fats,  and  carbohydrates.  These  food  materials 
may  be  burned  or  oxidized  outside  of  the  body,  and  the  heat  which 
they  yield  can  be  measured  directly.  Such  a  combustion  or  oxidation 
is  ordinarily  carried  out  in  the  laboratory  in  a  bomb  calorimeter  under 
high  oxygen  pressure,  and  it  is  by  such  a  method  of  combustion  or 
oxidation  that  the  heat  value  of  the  different  foodstuffs  is  estimated. 
If  a  definite  amount  of  a  piu-e  carbohydrate,  such  as  starch  or  sugar, 
is  burned  with  oxygen  in  a  calorimeter,  it  is  found  that  1  gram  of 
carbohydrate  yields  on  an  average  4100  calories,  or  4.1  large  calories. 
In  other  words,  the  4.1  large  calories  represent  the  combustion  equiv- 
alent of  a  gram  of  carbohydrate,  which  in  turn  is  a  measure  of  the 
amount  of  potential  energy  of  this  particular  form  of  foodstuff  which 
would  be  available  within  the  body  for  the  production  of  heat  or  for 
the  supply  of  energy  for  the  cells  or  tissues.  This  means  obviously 
that  the  end-products  in  the  oxidation  of  carbohydrate  are  the  same 
in  the  body  as  those  formed  by  combustion  outside  the  body.  If 
a  definite  amount  of  fat  is  burned  with  oxygen  in  a  calorimeter,  it 
is  found  on  an  average  that  1  gram  of  fat  yields  9300  calories  or 
9.3  large  calories.  This  figure,  like  the  corresponding  figure  obtained 
by  the  combustion  of  a  carbohydrate,  is  a  measure  of  the  amount  of 
potential  energy  which  this  form  of  foodstuff  is  capable  of  fiu-nishing 
for  the  production  of  heat  or  energy  in  the  body,  since  fat,  like  carbo- 
hydrate, biu-ns  to  the  same  end-products  by  oxidation  in  the  body 
as  in  combustion  outside  the  body.     In  considering  the  heat  value 


374  CHEMISTRY  OF  FOOD  AND  NUTRITION 

of  protein  as  utilized  in  the  body,  we  find  that  the  end-products  of 
its  oxidation  in  the  organism  are  carbon  dioxid  and  water,  together 
with  urea  and  some  other  nitrogenous  waste  products.  In  other 
words,  the  breaking  down  of  protein  in  the  body  is  not  as  complete  as 
is  the  combustion  of  protein  outside  of  the  body.  If  a  gram  of  protein, 
for  example,  is  burned  with  oxygen  in  a  calorimeter,  it  yields  on  an 
average  5778  calories.  When  burned  in  the  body,  however,  the  nitro- 
gen of  the  protein  molecule  is  eliminated  in  the  form  of  urea,  and 
there  are  also  certain  other  nitrogenous  products,  all  of  which  have 
heat  value  of  their  own.  If  it  is  assumed,  as  is  quite  proper  for 
such  a  purpose,  that  essentially  all  the  nitrogen  of  the  protein  broken 
down  in  the  body  appears  eventually  in  the  excreta  as  urea,  and  that 
one-third  gram  of  urea  results  from  the  breaking  down  of  one  gram  of 
protein,  we  may  deduct  the  heat  value  of  this  amount  of  urea  from 
the  combustion  equivalent  of  one  gram  of  protein,  with  the  result 
that  the  average  heat  value  to  the  body  for  one  gram  of  protein  is 
about  4100  calories,  or  4.1  large  calories. 

By  such  methods  the  heat  values  of  protein,  carbohydrate  and  fat, 
or  the  amount  of  potential  energy  which  these  foodstuffs  contain, 
available  for  supplying  the  energy  needs  of  the  body,  may  be  estimated. 
The  average  values  usually  made  use  of  by  physiologists  are  as  follows: 

1  gram  of  protein  =  4100  calories,  or  4.1  large  calories.  1  gram  of 
carbohydrate  =  4100  calories,  or  4.1  large  calories.  1  gram  of  fat  = 
9305  calories,  or  9.3  large  calories. 

It  is  obvious  from  these  statements  that,  knowing  the  composition 
of  any  given  food,  it  is  possible  to  calculate  its  heat  value  or  potential 
energy.  Since  our  food  is  in  a  sense  fuel  to  supply  the  energy  of  the 
body,  we  may  also  speak  of  these  values  as  fuel  values.  In  the  table 
already  presented,  showing  the  chemical  composition  of  some  common 
food  materials,  there  is  given  a  column  of  figures  showing  the  fuel  value 
per  pound  of  the  different  food  materials  expressed  in  calories.  It 
is  to  be  remembered,  however,  that  heat  value  or  fuel  value  of  a  food 
is  not  the  only  factor  to  be  considered  in  determining  food  value.  The 
nitrogen  content,  which  in  a  sense  is  a  measure  of  the  amount  of  pro- 
tein present,  is  likewise  essential.  Further,  there  are  many  minor 
factors  connected  with  our  food  material  which  must  be  given  consider- 
ation, since  man\'  of  such  minor  factors  are  of  importance,  and  some- 
times of  great  importance,  in  determining  nutritive  value. 

As  it  is  very  difficult,  in  many  cases  at  least,  to  determine  directly 
the  amount  of  protein  contained  in  any  foodstuff,  it  is  the  custom  to 
estimate  the  amount  of  protein  by  a  determination  of  the  amount  of 
nitrogen  contained  in  the  food  material.  As  has  already  been  stated, 
protein  on  an  average  contains  1(5  per  cent,  of  nitrogen.  Consequently, 
multiplying  the  percentage  of  nitrogen  contained  in  a  foodstuft'  by  the 
factor  f).25  gives  the  amount  of  protein.  It  is  easy  to  see  that  such 
an  estimate  is  not  always  quite  correct,  since  it  assumes  that  all  the 
nitrogen  in  foodstuff's  is  in  the  form  of  protein.    This  is  not  always 


CHEMISTRY  OF  FOOD  AND  NUTRITION  375 

the  case,  but  in  a  majority  of  foodstuft's  the  larger  percentage  of  nitro- 
gen is  protein  nitrogen,  and  consequently  this  method  is,  on  the  whole, 
fairly  satisfactory. 

Knowing  the  composition  of  foods,  especially  their  content  of  pro- 
tein and  their  fuel  value,  the  next  factor  to  consider  is,  how  far  foods 
are  capable  of  being  utilized  by  the  body.  It  is  frequently  stated  that 
the  body  is  not  nourished  by  what  is  eaten,  but  rather  by  what  is 
digested  and  absorbed,  for  not  everything  that  is  eaten  is  available 
for  the  needs  of  the  body.  There  is  always  the  question  of  utilization, 
of  the  relative  digestibility.  Physiologists  determine  the  degree  of 
utilization  of  any  given  food  by  a  simple  feeding  experiment,  either 
on  man  or  with  animals,  as  the  case  may  be.  The  food  is  carefully 
weighed  and  analyzed,  its  content  of  protein  or  nitrogen  and  fat  deter- 
mined, and  then  the  solid  excrement  is  collected  for  a  given  period, 
say  of  twenty-four  hours,  while  the  diet  in  question  is  being  taken.  The 
excrement  is  then  subjected  to  chemical  analysis  and  its  content  of 
nitrogen  and  fat  determined.  In  this  way,  by  comparison  of  the  intake 
of  nitrogen  and  fat  and  their  output  in  the  solid  excrement,  the  per- 
centage utilization  of  nitrogen  or  protein  and  of  fat  can  be  ascertained. 

For  130  days. 

Utilization  ot  Utilization  of 

nitrogen,  fat, 

Subject.                                                                                                      per  cent.  per  cent. 

1 89  98 

2 90  98 

3 89  97 

4 88  97 

5 88  97 

6 88  98 

In  the  above  table  are  the  data  connected  with  six  human  sub- 
jects, where  a  feeding  experiment  was  continued  for  130  days,  with 
a  view  to  determining  the  utilization  of  both  nitrogen  and  fat.  These 
figures  show  at  a  glance  that  in  this  particular  experiment  the  fat  of 
the  food  was  much  more  completely  absorbed  and  utilized  than  the 
nitrogen  or  protein  food.  In  other  words,  these  subjects  during  four 
months  utilized  practically  between  97  and  98  per  cent,  of  the  fat 
fed.  Of  nitrogen,  however,  only  88  to  90  per  cent,  was  utilized.  This 
relatively  low  utilization  of  nitrogen,  however,  w^as  due  to  the  character 
of  the  food,  which  was  largely  vegetable  in  its  nature.  It  is  a  well- 
understood  fact  that  the  easily  digestible  animal  foods,  such  as  meat, 
eggs,  milk,  etc.,  are  absorbed  or  utilized  up  to  even  99  per  cent.  In 
vegetable  foods,  however,  the  utilization  is  less  complete,  as  in  the 
above  table.  This  difference  in  the  utilization  of  vegetable  protein  is 
not  due  to  any  specific  peculiarity  of  the  vegetable  protein,  but  is  to 
be  attributed  to  the  general  character  of  vegetable  foodstuffs  with 
their  large  content  of  indigestible  cellulose  which  renders  the  digestion 
of  the  protein  relatively  difficult.  It  is  not  uncommon  to  find  with 
some  vegetable  foods  a  loss  through  the  feces  of  25  per  cent,  of  the 


r6 


CHEMISTRY  OF  FOOD  AND  NUTRITION 


protein  ingested.  Here,  however,  care  in  the  preparation  of  the  food 
counts  for  considerable.  Thorough  cooking  and  careful  preparation 
of  such  vegetable  products  result  frequently  in  raising  the  degree  of 
utilization. 

In  the  two  following  tables  are  sho\\ai  the  utilization  of  fat  and  of 
nitrogen  in  a  long  series  of  experiments  made  upon  dogs,  each  period 
covering  ten  days.  Here  the  food  fed  was  essentiall}^  the  same  in  com- 
position as  regards  the  content  of  nitrogen  or  protein  and  fat;  but  as 
the  experiment  progressed  the  proportion  of  vegetable  protein  was 
increased,  so  that  in  the  later  periods  the  food  was  almost  entii'ely  of 
vegetable  natiue.  It  will  be  observed  that  in  the  utilization  of  fat 
there  was  no  particular  difference  in  the  various  periods.  Thus,  in 
dog  5,  the  utilization  of  fat  varied  only  from  96  to  98  per  cent.  This 
holds  true  for  nearly  all  the  dogs.  In  some  one  period  there  may  be 
seen  a  decided  change,  but  in  general  the  utilization  of  fat  was  essen- 
tially the  same  for  a  given  dog  throughout  the  individual  periods.  In 
the  utilization  of  nitrogen  or  protein,  however,  the  result  was  differ- 
ent. In  most  cases,  as  the  experiment  progressed,  there  is  to  be 
observed  a  falling  oft'  in  the  utilization  of  nitrogen.  Thus,  in  dog  4, 
while  in  the  first  two  periods  of  ten  days  each  the  utilization  of  nitro- 
gen varied  from  94  to  95  per  cent.,  in  the  later  periods  it  gradually 
fell  as  the  proportion  of  vegetable  food  was  increased.  While  some 
exceptions  may  be  found  with  the  different  dogs,  yet  in  a  general  way 
this  same  tendency  is  seen  tlu*oughout  the  experiment. 

UTILIZATION   OF   FAT   IN   PERCENTAGES. 


Per 

lods 

1 

2 

3 

4 

Dogs 
5 

12 

13 

15 

17 

20 

1   . 

.   .   .  97 

96 

93 

97 

97 

96 

96 

98 

98 

95 

2 

.  96 

96 

98 

98 

98 

94 

95 

97 

98 

95 

3 

.  98 

97 

97 

99 

96 

97 

97 

98 

94 

98 

4 

.  98 

96 

97 

97 

96 

94 

95 

98 

97 

97 

5 

.  96 

94 

98 

97 

95 

95 

98 

97 

96 

6 

.  97 

98 

94 

98 

97 

96 

94 

97 

96 

97 

7 

97 

98 

98 

97 

96 

93 

95 

97 

98 

96 

8 

98 

96 

96 

96 

93 

97 

9 

98 

97 

98 

97 

98 

10 

98 

97 

98 

11 

97 

92 

97 

12 

97 

97 

UTILIZATION 

OF  NITROGEN  IN 

PERCENTAGES. 

Periods. 

1 

2 

3 

4 

Dogs. 
.5 

12 

13 

15 

17 

20 

1  ....  95 

91 

92 

94 

91 

91 

90 

93 

92 

91 

2 

92 

94 

94 

95 

93 

90 

92 

96 

92 

87 

3 

91 

92 

90 

91 

88 

89 

86 

95 

89 

91 

4 

90 

85 

90 

92 

91 

82 

83 

91 

83 

93 

5 

90 

82 

88 

92 

86 

85 

84 

96 

91 

90 

6 

86 

87 

89 

83 

86 

89 

87 

94 

91 

86 

7 

87 

87 

90 

83 

87 

83 

88 

90 

93 

91 

8 

90 

83 

84 

81 

89 

89 

9 

89 

87 

92 

87 

89 

10 

93 

85 

94 

11   . 

93 

81 

86 

12  . 

89 

92 

CHEMISTRY  OF  FOOD  AND  NUTRITION  377 

While  the  amount  of  nitrocfen  contained  in  the  solid  excrement  repre- 
sents mainly  undigested  or  unabsorl)ed  protein,  the  amount  of  nitro- 
gen contained  in  the  urine  represents,  on  the  other  hand,  the  amount 
of  protein  which  has  been  burned  up  in  the  body  or  metalnjlized. 
Hence,  collection  of  the  urine  during  a  given  period  and  determination 
of  the  content  of  nitrogen  is  the  means  by  which  the  physiologist  deter- 
mines the  extent  to  which  the  protein  food  or  the  protein  of  the  body 
tissues  is  metabolized.  The  amount  of  nitrogen  in  the  feces  represents 
mainly  undigested  protein.  The  amount  in  the  urine  represents  pro- 
tein which  has  been  utilized  or  metabolized.  If  the  urine  of  twenty- 
four  hours  shows  on  analysis,  a  content  of  16  grams  of  nitrogen,  this 
means  that  there  has  been  broken  down  in  the  body  during  that  period 
16  X  6.25  =  100  grams  of  protein  material.  It  is  to  be  remembered, 
as  previously  stated,  that  protein  contains  on  an  average  16  per  cent, 
of  nitrogen,  and  as  practically  all  the  nitrogen  coming  from  the  break- 
ing down  of  protein  in  the  body  is  excreted  through  the  urine  it  is 
apparent  that  the  amount  of  nitrogen  contained  in  the  urine  in  a  given 
period,  multiplied  by  the  factor  6.25,  gives  the  amount  of  protein 
broken  down  or  metabolized  in  the  body  during  that  period. 

If  the  total  nitrogen  of  the  food  intake  during  a  given  period  amounts 
to  more  than  the  total  nitrogen  of  the  feces  and  of  the  urine  for  the 
same  period,  it  is  plain  that  the  diflFerence  must  represent  nitrogen  or 
protein  which  has  been  stored  up  in  the  body.  On  the  other  hand,  if 
the  nitrogen  of  the  urine  and  feces  during  a  given  period  amounts  to 
more  than  the  nitrogen  of  the  food  ingested  during  that  same  period, 
then  it  is  evident  that  the  body  must  be  losing  nitrogen  from  the  break- 
ing down  of  tissue  protein.  In  other  words,  under  these  last  condi- 
tions the  body  is  not  being  fed  sufficient  food  material  to  meet  the 
needs  of  the  body,  and  hence  the  body  is  compelled  to  draw  upon  its 
own  tissues  to  supply  its  needs.  By  methods  such  as  these  it  is  possible 
to  strike  a  balance  which  will  determine  whether  the  body  is  taking 
on  or  losing  nitrogen.  If  the  balance  is  even,  the  body  is  in  what  is 
termed  nitrogen  equilibrium,  which  means  that  it  is  receiving  in  the 
food  as  much  protein  nitrogen  as  it  is  metabolizing  in  the  body  and 
eliminating  in  the  excreta.  If  there  is  a  plus  balance  in  favor  of  the 
food,  it  is  clear  that  the  body  is  laying  on  or  storing  protein.  If,  on 
the  other  hand,  the  nitrogen  balance  is  a  minus  one,  the  body  must 
plainly  be  losing  protein.  During  the  period  of  growth  or  in  the 
recovery  from  wasting  diseases,  such  as  fevers,  etc.,  the  body  tends 
to  store  protein,  and  under  such  conditions  the  balance  obviously 
would  be  in  favor  of  the  food  nitrogen.  Throughout  adult  life,  how- 
ever, the  diet  is  usually  regulated,  consciously  or  unconsciously, 
under  normal  conditions,  so  that  nitrogen  equilibrium  is  generally 
maintained  through  relatively  long  periods  of  time. 

A  person  may  be  in  nitrogen  equilibrium  and  yet  gain  or  lose  in 
body  weight.  This  may  be  due  to  a  lack  of  carbon  equilibrium,  to  a 
gain  or  loss  of  fat,  for  example,  although  it  may  equally  well  be  due  to 


378  CHEMISTRY  OF  FOOD  AND  NUTRITION 

changes  in  the  content  of  water  in  the  tissues  of  the  body.  In  body 
equihbrium,  body  weight  obviously  would  remain  practically  sta- 
tionary, although  it  is  plain  that  under  such  conditions  there  might  be 
a  lack  of  nitrogen  equilibrium.  In  carbon  equilibrium  the  total  carbon 
of  the  excreta,  namely,  carbon  dioxid  in  the  expired  air,  the  carbon 
of  the  organic  substances  contained  in  the  urine  and  in  the  solid  excre- 
ment would  be  balanced  by  the  intake  of  carbon  with  the  food.  Plainly, 
a  person  may  lose  or  gain  in  carbon,  while  the  nitrogen  is  essentially 
in  equilibrium.  Theoretically,  one  may  have  a  water  equilibrium 
or  an  equilibrium  of  inorganic  salts,  but  such  conditions  have  little 
physiological  significance.  The  three  important  conditions  to  be  con- 
sidered are  nitrogen  equilibrium,  carbon  equilibrium,  and  body  equi- 
librium. Carbon  equilibrium  can  be  determined  by  the  use  of  a  respi- 
ration chamber,  in  which  the  subject  under  examination  lives  under 
conditions  where  the  total  quantity  of  carbon  dioxid  given  off  from 
the  lungs  and  through  the  skin  can  be  accurately  determined.  In  such 
an  apparatus,  or  air-tight  chamber,  air  is  dra\^^l  through  the  apparatus 
by  means  of  a  pump,  the  total  amount  of  air  passing  through  being 
measured  by  a  gasometer.  Definite  fractions  of  the  air  obviously 
can  be  drawn  off  from  time  to  time  and  analyzed  for  carbon  dioxid. 
The  m-ine  and  faeces  are  collected  and  analyzed,  while  at  the  same  time 
the  intake  of  food  is  measured  and  the  content  of  protein,  fat  and  carbo- 
hydrate determined.  In  this  way  it  is  possible  to  make  not  merely 
a  balance  of  the  intake  and  output  of  carbon,  but  a  complete  balance 
may  be  struck  in  which  both  carbon  and  nitrogen  balances  can  be  esti- 
mated, as  well  as  changes  in  body  weight.  Under  ordinary  conditions 
adult  persons  usually  live  so  that  they  maintain  a  general  body  equil- 
ibrium; that  is,  the  ingesta  of  all  kinds  are  balanced  by  the  corre- 
sponding excretions,  the  individual  maintaining  practically  constant 
body  weight. 

We  now  come  to  what  constitutes  a  very  important  and  significant 
property  of  protein  food,  viz.,  that  protein  or  nitrogen  equilibrium 
can  be  maintained  at  different  levels  of  nitrogen  intake.  If  a  person 
is  in  a  semifasting  condition,  eating  each  day  a  much  smaller  amount 
of  protein  food  than  the  needs  of  his  body  demand,  it  would  naturally 
be  expected  that  if  the  intake  of  protein  food  is  considerably  increased 
the  body  would  hold  on  to  the  larger  portion  of  the  increased  protein, 
but  such  is  not  the  case.  Experiment  shows  that  under  such  conditions 
where  the  body  is  practically  living  in  large  measure  on  the  protein 
of  its  own  tissues,  the  extra  protein  fed  is  at  once  metabolized  in  the 
body,  the  nitrogen  at  once  eliminated,  instead  of  being  stored  up  in 
the  tissues,  and  nitrogen  equilibrium  is  established  at  a  higher  level. 
In  other  words,  protein  food  actually  tends  to  increase  metabolism 
in  the  tissues.  This  property  is  usually  s})oken  of  as  the  ''specific 
dynamic  action"  of  protein.  This  stimulation  of  the  metabolic  pro- 
cesses of  the  body  shows  itself  not  only  in  increasing  the  output  of 
nitrogen,  signifying  increased  breaking  down  of  protein,  but  it  is  accom- 


CHEMISTRY  OF  FOOD  AND  NUTRITION  379 

panied  likewise  by  an  increased  metabolism  of  the  fats  and  carbo- 
hydrates of  the  body. 

Body           Nitrogen  of  Nitrogen  Nitrogen 

weight,  the  food,  excreted,  balance 

Date.                                                 kilos.  grams.  grams.  grams. 

Nov.  6 65.4  2.69  8.31  -  5.62 

7 65.4  2.69  5.37  -  2.68 

8 65.1  2.69  5.71  -  3.02 

9 65.3  2.69  4.88  -  2.19 

10 65.0  2.69  4.32  -  1.63 

11 64.9       2.69  4.25  -  1.56 

12 64.9       2.69  4.47  -  1.78 

13 64.6       2.96  4.88  -  1.92 

14 64.4       2.96  4.30  -  1.44 

15 64.3       2.96  4.75  -  1.79 

16  .   r   .   .   .   .   64.4       2.96  4.36  -  1.40 

17 64.4       2.96  4.13  -  1.17 

18 64.4       2.96  4.35  -  1.39 

19 64.4       2.96  4.32  -  1.36 

20 64.4       2.96  4.22  -  1.26 

21 64.0       2.96  4.06  -  1.10 


22 64.1  4.02  4.22 

23 64.4  4.02  4.35 

24  .....   .  64.4  4.02  4.21 

25 64.4  4.02  4.40 


26 64.2  8.24  6.56 

27 64.4  13.45  8.67 

28 64.4  13.66  10.54 

29 64.0  13.45  11.10 

30 64.2  13.24  12.83 

Dec.  1 64.2  13.24  11.70 

2 63.9  12.61  12.00 


3 64.0  22.93  16.24 

4 63.9  22.41  21.47 

5 63.9  22.41  23.10 

6 63.6  23.35  23.12 

7 63.9  23.04  22.82 

8 63.8  22.62  22.86 

+  6.15 

In  the  above  table  are  given  the  results  of  a  series  of  observations 
made  by  Siven  on  himself.  The  table  shows  body  weight,  the  amount 
of  nitrogen  in  the  daily  food,  the  amount  of  nitrogen  excreted  through 
the  urine  and  feces,  and  the  nitrogen  balance,  for  every  day  through 
a  period  covering  more  than  a  month.  The  amount  of  non-nitrogenous 
food  taken  is  not  specified,  but  it  was  not  excessive  in  quantity.  During 
the  first  period  from  November  6  to  21,  the  amount  of  protein  food 
ingested  daily  was  very  small,  namely,  2.9  grams  of  nitrogen,  equal 
to  about  18  grams  of  protein.  During  this  period  it  will  be  observed 
that  the  nitrogen  excreted  daily  through  both  the  urine  and  feces 


-31. 

31 

_ 

0. 

20 

— 

0, 

33 

— 

0 

19 

- 

0. 

,38 

- 

1, 

,10 

+ 

1 

.68 

+ 

4 

,78 

+ 

3 

.12 

+ 

2 

.35 

+ 

0 

.41 

+ 

1 

.54 

+ 

0 

.61 

+  14 

.49 

+ 

6 

.69 

+ 

0 

.94 

— 

0 

.69 

+ 

0 

.23 

+ 

0 

.22 

— 

0 

.24 

380  CHEMISTRY  OF  FOOD  AND  NUTRITION 

amounted  to  over  4  grams  per  day,  which  means  that  the  body  was 
breakmg  down  protehi  tissue  equal  to  between  25  and  30  grams.  The 
daily  nitrogen  balance  during  this  period  was  a  minus  one,  amounting 
to  more  than  a  gram  of  nitrogen  per  day  during  the  latter  part  of  the 
period.  At  the  same  time,  it  will  be  observed  that  the  body  weight 
was  practically  constant  during  the  last  ten  days.  On  November  22, 
the  intake  of  nitrogen  was  increased  to  4  grams,  equal  to  25  grams  of 
protein  food.  Under  these  conditions  the  body  weight  remained  as 
before  and  the  nitrogen  excreted  was  slightly  in  excess  of  the  nitrogen 
ingested.  The  minus  balance  was  a  very  small  one,  equal  to  only  a 
third  of  a  gram  of  nitrogen  per  day.  On  November  26,  the  protein 
food  was  increased  in  amount,  so  that  the  nitrogen  ingested  was  8.24 
grams.  On  this  day  there  was  a  decided  plus  nitrogen  balance.  On 
the  following  days  it  is  to  be  noted  that  each  increase  in  the  amount  of 
nitrogenous  food  ingested  is  accompanied  by  a  corresponding  increase 
in  the  amount  of  nitrogen  excreted,  accompanied  on  most  days  by  a 
plus  nitrogen  balance.  Yet  it  is  to  be  observed  on  December  5  and 
December  8,  when  22  grams  of  nitrogen  were  consumed  daily,  there 
was  still  a  minus  nitrogen  balance. 

The  main  point,  however,  to  be  emphasized  in  connection  with  these 
data  is  that  there  is  a  certain  low  limit  of  protein  which  just  suffices 
to  maintain  nitrogen  equilibrium.  Beyond  this  point,  up  to  the  limit 
of  the  capacity  of  the  body  to  digest  and  absorb  protein  food,  there 
is  always  a  tendency  for  nitrogen  equilibrium  to  be  maintained.  Thus, 
it  is  seen  in  these  experiments  that  with  an  intake  of  13  grams  of  nitro- 
gen, the  plus  nitrogen  balance  is  just  as  large,  or  even  larger,  than  with 
an  intake  of  23  grams  of  nitrogen  daily.  Further,  it  is  to  be  noted 
that  with  increase  of  protein  food  to  the  limit  recorded  in  these  experi- 
ments as  on  December  5  and  6,  body  weight  tends  to  diminish  rather 
than  increase.  This  is  in  harmony  with  the  statement  already  made, 
that  protein  food  tends  to  increase  not  only  the  rate  of  protein  metab- 
olism, but  likewise  tends  to  increase  the  rate  of  carbon  metabolism 
or  the  metabolism  of  fat  and  carbohydrate.  Plainly,  one  may  ask 
the  question,  What  level  of  protein  or  nitrogen  intake  is  most  desirable 
for  the  maintenance  of  the  best  condition  of  health?  Increasing  the 
amount  of  protein  food  appears  to  result  in  increasing  the  rate  at  which 
proteins,  fats  and  carbohydrates  are  broken  down,  and  is  not  accom- 
panied by  any  appreciable  storing  of  protein  for  the  future  needs  of 
the  body.  Further,  since  increase  of  protein  food  is  accompanied  by 
a  corresponding  increase  in  the  excretion  of  nitrogenous  waste  products, 
it  is  o})vious  that  under  such  conditions  considerable  energy  must  be 
wasted  in  the  excretion  of  this  added  waste.  Unless  the  body  in  some 
manner  derives  special  benefit  from  the  non-nitrogenous  part  of  the 
protein  molecule,  there  would  seem  to  be  no  good  reason  for  the  daily 
consumption  of  these  larger  amounts  of  protein  food  far  beyond  what 
is  necessary  to  maintain  nitrogen  equilibrium. 

In  this  connection  it  is  well  to  emphasize  the  effect  of  non-nitro- 
genous foods  on  the  rate  of  protein  metabolism.    Both  fats  and  carbo- 


CHEMISTRY  OF  FOOD  AND  NUT  HIT  ION  381 

hydrates  tend  to  lower  the  rate  at  which  protein  undergoes  metaboHsm; 
or,  in  other  words,  they  protect  the  protein  of  the  food  and  of  the 
tissues.  If  an  animal,  for  example,  is  brought  into  a  condition  of 
nitrogen  equilibrium  on  protein  food  alone,  the  addition  of  a  non- 
protein foodstuflf,  such  as  fat  or  carbohydrate,  reduces  considerably 
the  amount  of  protein  necessary  to  maintain  nitrogen  equilibrium. 
Fats  and  carbohydrates  therefore  are  protein-sparers,  and  this  is  one 
of  the  important  points  connected  with  their  nutritional  value. 

In  the  following  data  from  experiments  made  by  Voit  on  dogs,  it 
is  to  be  observed  that  the  addition  of  150  grams  of  fat  to  the  1500  grams 
of  meat  fed  resulted  in  a  sparing  effect  on  protein  or  flesh  metabolized 
amounting  to  38  grams.  In  the  second  experiment,  where  only  500 
grams  of  meat  were  fed,  the  addition  of  100  grams  of  fat  resulted  in 
the  sparing  of  36  grams  of  protein.  The  radical  point  of  difference  in 
the  two  experiments  is  the  amount  of  protein  ingested.  As  has  already 
been  stated,  protein  food  stimulates  protein  metabolism;  it  likewise 
accelerates  the  metabolism  of  non-nitrogenous  matter.  Consequently, 
the  sparing  or  protecting  eflfect  of  the  fat  is  most  conspicuous  where 
the  intake  of  protein  is  relatively  small.  In  other  words,  100  grams  of 
fat  taken  in  conjunction  with  500  grams  of  meat  exercises  practically 
as  great  a  sparing  effect  on  protein  as  150  grams  of  fat  when  fed  in 
connection  with  1500  grams  of  meat. 

Food.  Flesh. 


Meat, 

Fat, 

M 

etabolized, 

On  the  b( 

grams. 

grams. 

grams. 

grams 

1500 

0 

1512 

-12 

1500 

150 

1474 

•    +26 

500 

0 

556 

-56 

500 

100 

520 

-20 

When  carbohydrate  is  added  to  a  meat  diet,  there  is  at  once  a  saving 
in  the  decomposition  of  protein,  as  show^n  in  the  following  figures 
covering  an  experiment  of  two  days: 

Meat,  Sugar,  Flesh  metabolized, 

grams.  grams.  grams. 

500  200  502    ' 

500  0  564 

Without  the  sugar  there  w^ere  64  grams  of  protein  metabolized  in 
excess  of  the  protein  fed,  but  addition  of  the  200  grams  of  sugar  caused 
practically  a  saving  of  all  this  with  formation  of  essentially  a  nitrogen 
balance. 

The  sparing  of  protein  by  carbohydrate  is  greater  than  by  fats; 
a  fact  of  considerable  dietetic  importance,  and  it  is  well  illustrated  by 
the  following  experiments  taken  from  Voit: 


Food. 

Flesh. 

Meat, 

Non-nitrogenous  food. 

Metabolized, 

Balance  in  the  body, 

grams. 

grams. 

grams. 

grams. 

500 

250 

fat 

558 

-   58 

500 

300 

sugar 

466 

+  34 

500 

200 

sugar 

505 

-     5 

800 

250 

starch 

745 

+  55 

800 

200 

fat 

773 

+  27 

2000 

200-300  starch 

1792 

+208 

2000 

250 

fat 

•    1883 

+  117 

382  CHEMISTRY  OF  FOOD  AND  NUTRITION 

111  considering;  the  results  of  this  experiment,  it  is  to  be  remembered 
that  the  calorific  or  fuel  value  of  fat  as  compared  with  carbohydrate 
is  as  9.3  to  4.1.  In  spite  of  this  fact,  it  is  clearly  evident  that  the  sugar 
and  starch  are  far  more  efficient  than  fat  in  protecting  protein.  Thus, 
with  the  income  of  500  grams  of  meat  and  250  grams  of  fat,  the  body 
of  the  animal  lost  58  grams  of  protein;  while  with  a  like  amount  of 
meat  and  300  grams  of  sugar  the  body  not  only  saved  the  58  grams  of 
protein,  but  in  addition  stored  up  34  grams,  showing  a  plus  balance 
to  that  extent.  Again,  with  2000  grams  of  meat,  the  plus  protein  bal- 
ance with  the  starch  was  considerably  greater  than  the  plus  balance 
with  250  grams  of  fat. 

It  is  plain  from  the  foregoing  that  on  a  mixed  diet  of  protein  and  non- 
nitrogenous  food,  the  proportion  of  the  latter  may  be  increased  and 
that  of  the  former  decreased  to  a  marked  degree  without  causing  a 
loss  of  protein  tissue  from  the  body.  As  already  stated  in  other  con- 
nections, food  fulfils  two  distinct  purposes.  It  furnishes  the  material 
for  the  formation  of  new  living  matter,  or  the  replacement  of  that  which 
is  continually'  being  lost.  In  addition,  it  furnishes  a  supply  of  energy 
for  the  work  done  by  the  various  cells  of  the  body,  the  contraction 
of  the  muscles,  the  secretion  of  the  glands,  the  discharges  of  the  nerve 
cells,  etc.  For  the  first  function,  protein  is  absolutely  needed,  and  per- 
haps it  is  the  only  form  of  food  that  is  needed ;  but  for  the  second  func- 
tion, that  is,  the  energy  requirements,  this  may  be  met  by  any  of  the 
three  energy-yielding  foodstuffs,  i.  e.,  carbohydrates,  fats,  or  proteins, 
especially  by  the  carboh^'drates.  If  the  supply  of  non-protein  material 
is  relatively  large,  then,  as  we  have  seen,  the  amount  of  protein  food  can 
be  lowered  to  a  certain  minimum,  which  is  plainly  required  for  the 
construction  of  the  living  materials  of  the  cells  and  tissues  of  the  body. 

Part  XL 

It  is  plain  from  what  has  already  been  stated  that  the  two  non- 
nitrogenous  foods,  fat  and  carbohydrate,  play  a  very  important  part 
in  nutrition,  because  of  their  ability  to  protect  in  a  measure  the 
integrity  of  tissue  protein.  When  it  is  remembered  that  a  diet  of 
pure  protein,  such  as  meat  or  eggs,  must  be  excessive  in  quantity 
in  order  to  meet  the  energy  requirements  of  the  body  and  that  the 
stimulating  action  of  ])rotein  food  serves  to  whip  up  body  metabolism, 
it  may  be  ajipreciated  at  full  measure  the  great  physiological  saving 
which  results  from  the  addition  of  carbohydrate  and  fat  to  the  daily  diet. 
The  establishment  of  nitrogenous  equilibrium  is  made  possible  at  a  much 
lower  level  by  the  judicious  addition  of  these  two  non-nitrogenous 
fooflstufi's.  Further,  it  has  been  made  clear  that  a  certain  minimum 
amount  of  protein  food  is  necessary  for  the  construction  and  main- 
tenance of  the  living  protoplasm  of  the  cells  and  tissues  of  the  body. 

We  may  next  consider  whether  there  is  any  truth  in  the  old-time 
belief  that  protein  or  nitrogenous  foods  are  essential  for  muscular 
activity;  or  in  other  words,  that  the  .source  of  muscular  energy  is  to  be 


CHEMISTRY  OF  FOOD  AND  NUTRITION  383 

found  in  the  metabolism  of  protein  material.  This  view,  which  was 
originally  enunciated  l)y  Liebig,  was  based  on  the  principle  that  proteins 
were  plastic  foods;  that  is,  they  had  to  do  with  the  construction  of  the 
protein  tissues,  and  that  consequently  protein  must  be  the  material 
burned  up  or  oxidized  when  muscles  are  active.  Experiments  carried 
on  by  many  physiologists  have  shown,  however,  quite  conclusively 
that  protein  is  certainly  not  the  sole  source  of  muscular  energy.  One 
of  the  early  experiments  bearing  on  this  question  was  carried  out  by 
two  German  physiologists,  Fick  and  Wislicenus.  These  two  experi- 
menters ascended  a  high  mountain,  and  knowing  the  weight  of  their 
bodies,  it  was  possible  to  estimate  how  much  work  was  done  in  ascend- 
ing this  mountain  to  a  height  of  nearly  2000  meters.  Prior  to  the 
ascent,  the  food  consumed  by  these  men  was  entirely  non-nitrogenous, 
and  during  the  climb  of  eight  hours,  and  for  six  hours  afterward,  the 
food  was  likewise  non-nitrogenous.  The  urine  was  collected  and  the 
nitrogen  determined,  from  which  it  was  easy  to  estimate  the  amount 
of  protein  that  had  been  destroyed.  It  was  found  that  the  energy 
contained  in  the  protein  broken  down  was  quite  inadequate  to  account 
for  the  work  done,  and  their  calculation  left  out  of  consideration  entirely 
the  amount  of  work  done  by  the  heart  and  respiratory  muscles. 

Experiments  made  upon  dogs  working  in  a  treadwheel  and  upon 
men  performing  work  while  in  a  respiration  chamber  have  all  given 
data  showing  that  the  energy  of  the  muscular  work  performed  was  far 
in  excess  of  the  heat  energy  of  the  protein  oxidized  during  the  period 
or  periods.  Further,  experiments  made  upon  soldiers  and  others  while 
resting  and  performing  long  marches  have  shown  that  there  is  no  dis- 
tinct increase  in  the  excretion  of  nitrogen  after  muscular  exercise. 
The  only  conditions  under  which  muscular  work  appears  to  be  accom- 
panied by  an  increased  excretion  of  nitrogen  is  when  the  subject  is 
taking  a  very  small  am.ount  of  non-nitrogenous  food,  or  when  the  work 
performed  is  very  excessive.  The  facts  apparently  are  that  the  muscle 
is  a  protein  machine  for  the  accomplishment  of  work,  but  in  the  ordi- 
nary performance  of  work  there  is  apparently  no  greater  wear  or  tear 
of  the  machinery;  that  is,  no  greater  tissue  waste,  than  when  the  muscle 
is  in  a  resting  condition. 

Whenever  a  person  performs  muscular  work,  it  is  obvious  that  some 
material  must  be  burned  up  in  order  to  provide  the  energy,  and  since 
this  material  is  apparently  not  protein,  it  is  plain  that  it  must  be 
some  non-nitrogenous  material.  Experiment  shows  that  when  muscles 
are  made  to  work  there  is  at  once  an  increased  output  of  carbon  dioxid, 
accompanied  by  an  increased  consumption  of  oxygen.  This  is  well 
illustrated  in  the  following  experiment  taken  from  Benedict  and 
Carpenter : 

CO2  U2  Heat 

eliminated,  absorbed,  produced, 

grams.  grams.  calories. 

Man  at  rest,  sleeping        ....  23  21  71 

Man  at  rest,  sitting 33  27  97 

Man  at  rest,  standing       ....  37  31  114 

Man  during  severe  work        .      .      .  248  213  653 


3S4 


CHEMISTRY  OF  FOOD  AND  NUTRITION 


111  the  above  experiment  the  effect  of  severe  work,  as  compared 
with  the  other  conditions,  is  very  marked,  both  in  the  amomit  of  carbon 
dioxid  (CO2)  eliminated  and  in  the  amount  of  oxygen  (O2)  absorbed. 
It  is  perfectly  clear  from  these  results  that  the  output  of  carbon  dioxid, 
which  means  the  breaking  down  of  carbonaceous  material,  must  vary 
enormously  during  the  day  with  variations  in  the  muscular  activity 
of  the  body.  The  one  important  factor  influencing  the  oxygen  and 
carbon  dioxid  exchange  in  the  lungs,  i.  e.,  the  extent  of  the  respira- 
tory interchange  is  muscular  activity.  In  muscular  work  respiration 
is  increased  in  frequency  and  in  depth.  The  volume  of  air  exchanged 
in  the  lungs  during  severe  labor  may  be  increased  sevenfold,  while  the 
oxygen  consumption  and  carbon  dioxid  excretion  are  frequently  in- 
creased seven  to  ten  times.    The  following  figures  may  be  given  as  an 


Oxygen  consumption  in  cubic  centimeters. 

Form  of  work. 

Total. 

After  deducting  value  for  rest. 

Respiratory 
quotient.    - 

Total. 

For  each  kilo 

of  moving 

weight. 

Standing  at  rest       .      .      . 

Walking  on  a  level 

Climbing 

263.75 

763.00             499.25 
1253.20              989.45 

8.990 
17.819 

0.801 
0.805 
0.801 

added  illustration,  showing  the  effect  on  oxygen  consumption  of 
walking  on  a  level  and  climbing,  the  subject  being  a  man  of  55.5 
kilos  body  weight.  The  figures  given  are  values  for  one  minute.  These 
data  simply  afford  another  striking  illustration  of  the  influence  of 
muscular  activity  upon  the  exchange  of  matter  in  the  body,  and  con- 
firm what  has  already  been  stated  many  times  that  oxidation,  espe- 
cially the  oxidation  of  fat  and  carbohydrate,  b}^  which  large  quantities 
of  heat  are  set  free,  easily  convertible  into  mechanical  energy,  is  a 
primary  factor  in  those  metabolic  processes  by  which  the  machinery 
of  tlie  lix'ing  man  is  able  to  work  so  efficiently. 

It  is  plain  from  what  has  been  said  that  muscular  work  as  carried 
on  under  ordinary  conditions  calls  for  carbohydrate  and  fat  in  the 
daily  diet  rather  than  for  protein.  Protein  metabolism  is  not  increased 
by  work,  providing  sufficient  non-])rotein  food  is  being  eaten.  This 
means  j>lainly  that  excessive  eating  of  i)rotein  food,  meats  and  kindred 
products,  is  not  necessary  for  the  doing  of  muscular  work.  There 
must  obviously  be  sufficient  protein  in  the  daily  diet  to  meet  the 
needs  of  the  cells  of  the  Ixxly  to  keep  the  machine  in  good  working  order, 
but  the  energ}^  called  for  in  even  excessive  muscular  work,  is  derived 
ordinarily  and  most  advantageously  from  carbohydrates  and  fats. 

A  mixed  diet,  one  which  contains  protein,  fat  and  carbohydrate, 


CHEMISTRY  OF  FOOD  AND  NUTRITION  385 

together  with  salts  and  ^^'ater,  is  the  most  beneficial  to  the  })ody  and 
one  which  accords  witli  physiological  experience.  As  stated  many 
times,  a  certain  amount  of  protein  food  is  needed  for  the  construction 
and  maintenance  of  cell  protoplasm;  fats  and  carbohydrates  are 
required  to  supply  the  energy  needs  of  the  body.  Fats  and  carbohy- 
drates may  be  substituted  one  for  the  other  in  some  measure,  but 
carbohydrates,  for  many  reasons,  constitute  the  larger  proportion  of 
the  non-nitrogenous  food  with  most  peoples.  This  is  due  not  alone 
to  the  fact  that  carbohydrates  are  relatively  easy  of  digestion  and  oxida- 
tion, but  also  because  of  the  abundance  and  consequent  cheapness  of 
carbohydrates  as  a  class.  A  study  of  the  dietary  habits  of  peoples 
throughout  the  world  has  shown  that  in  most  countries  carbohydrates 
are  usually  present  in  the  daily  diet  in  amounts  five  to  ten  times 
greater  than  the  quantity  of  fat.  From  an  energy  standpoint,  as 
already  explained,  one  part  of  fat  is  the  equal  of  2.3  parts  of  carbo- 
hydrate, such  as  sugar  or  starch.  Consequently,  in  the  replacing  of 
starch  by  fat,  or  vice  versa,  they  must  be  substituted  one  for  the  other 
in  isodynamic  amounts;  that  is,  1  gram  of  fat  will  take  the  place  of  2.3 
grams  of  sugar,  so  far  as  the  yield  of  energy^  is  concerned. 

The  average  daily  diet  with  its  heat  value,  advocated  by  the  cele- 
brated physiologist  Voit,  of  Germany,  is  as  follows: 

Grams.  Calories. 

Protein 118  483     " 

Fats 56  520 

Carbohydrates 500  2050 

3055 
Ranke,  on  the  other  hand,  recommended  a  diet  composed  as  follows: 

Grams.  Calories. 

Protein 100  410 

Fats 100  930 

Carbohydrates 240  984 

2324 

Moleschott,  another  authority  often  quoted,  gave  the  following  data 
as  representing  an  average  daily  diet: 

Grams.  Calories. 

Protein 130  533 

Fats 40  372 

Carbohydrates 550  2275 

3180 

From  these  statements  it  is  apparent  that  the  authorities  quoted 
considered  that  man  needs  approximately  100  to  130  grams  of  protein 
food  a  day,  with  sufficient  fat  and  carbohydrate  to  make  a  fuel  value 
ranging  from  2300  to  3100  calories.  It  is  obvious,  however,  that  the 
calorific  value  of  the  daily  food,  so  far  as  the  physiological  needs  are 
25 


386  CHEMISTRY  OF  FOOD  AND  NUTRITION 

concerned,  must  vary  with  the  degree  of  physical  activity.  Where  a 
large  amount  of  muscular  work  is  performed  there  is  need  for  a  corre- 
sponding increase  in  the  non-nitrogenous  foods,  and  since,  as  before 
stated,  carbohydrates  are  both  cheap  and  easily  digestible,  the  increase 
usually  comes  from  this  class  of  foods. 

A  study  of  the  table  showing  the  chemical  composition  of  some 
common  food  materials  given  on  page  369  shows  at  once  the 
advantages  of  a  mixed  diet  for  meeting  the  needs  of  the  body  for 
protein  and  total  energy.  Assuming  the  Voit  standard  to  represent 
the  daily  needs  of  the  adult,  namely,  118  grams  of  protein  with  a  total 
fuel  value  of  3053  calories,  it  is  apparent  that  animal  food,  such  as 
meat,  would  by  itself  be  quite  impossible  for  a  steady  diet.  As  fresh 
beef  contains  22  per  cent,  of  protein,  it  would  be  necessary  for  a  person 
to  eat  500  grams,  or  a  little  more  than  a  pound,  of  beef  to  obtain  the 
needed  118  grams  of  protein,  but  the  fuel  value  of  one  pound  of  beef 
is  only  540  calories.  Consequently,  in  order  to  obtain  the  necessary 
3000  calories,  at  least  six  pounds  of  beef  would  be  required,  or  six 
times  the  amount  of  protein  food  really  needed.  This,  plainly,  would 
be  physiologically  undesirable  and  exceedingly  uneconomical.  If,  on 
the  other  hand,  bread  with  a  fuel  value  of  1395  calories  per  pound, 
macaroni  with  1665  calories  per  pound,  or  rice  with  1630  calories  per 
pound,  are  used  to  replace  the  larger  portion  of  the  meat,  a  mixture  can 
be  obtained  much  more  advantageous  as  a  daily  diet. 

In  other  words,  almost  any  single  food,  if  eaten  in  sufficient  quantity 
to  supply  the  nitrogen  or  protein  requirements  of  the  body,  will  give 
either  too  little  or  too  great  fuel  value.  A  typical  animal  food,  such  as 
meat  or  eggs,  when  eaten  in  such  amount  as  will  furnish  the  neces- 
sary nitrogen  or  protein,  fails  to  furnish  more  than  a  fifth  of  the  fuel 
value  required.  As  a  rule  a  diet  made  up  solely  of  vegetable  foods, 
consumed  in  such  quantity  as  to  furnish  the  necessary  protein,  means 
the  consumption  of  much  more  carbohydrate  or  total  fuel  value  than 
the  body  really  needs.  There  are,  to  be  sure,  certain  vegetable  foods, 
apparent  from  the  table  of  food  compositions,  which  may  advanta- 
geously be  used  for  supplying  both  the  nitrogen  and  energy  require- 
ments. Practically,  however,  most  people  are  accustomed  to  obtain 
their  supply  of  proteins,  fats  and  carbohydrates  from  both  animal  and 
vegetable  foods.  It  is  a  fact  well  appreciated  by  physiologists  that 
the  mechanism  of  digestion  and  nutrition  as  a  whole  should  not  be 
subjected  to  undue  strain.  Consequently,  the  danger  of  consuming 
too  large  amounts  of  any  one  class  of  foods  is  just  as  serious  as  the 
danger  of  not  consuming  enough  to  meet  the  real  needs  of  the  body. 
The  protein  of  the  day's  diet  may  well  come  frbm  meat,  milk,  rice, 
bread,  potatoes,  and  other  vegeta})l('s,  thereby  introducing  along 
with  the  nitrogen,  (luantities  of  carbohydrate  and  fat  by  which  the 
protein  requirement  and  the  body  requirement  can  both  be  met  with- 
out consumption  of  an  undue  quantity  of  any  one  of  the  several 
classes  of  foodstufi's. 


CHEMISTRY  OF  FOOD  AND  NUTRITION 


387 


The  two  following  ta))les,  giving  the  average  food  consumption  of 
peoples  in  Swetleii  and  Finland,  are  well  worthy  of  study  as  showing 
first  the  different  foodstuffs  made  use  of  during  a  single  week,  the 
distribution  of  the  protein  in  the  form  of  vegetable  and  animal  pro- 
ducts, as  well  as  the  amounts  of  fat  and  carbohydrate  with  total  fuel 
values  for  a  week,  from  which  is  calculated  the  average  daily  consump- 
tion per  individual. 

SWEDISH— PER   WEEK. 


Food. 


Total 
amount, 
grams. 


Protein, 

grams. 


Fat, 
grams. 


Carbo- 
hydrate, 
grams. 


Calories. 


Rye  flour 
Wheat  flour 
Scotch  barley     . 
Oatmeal 

Peas 

Potatoes 

Skimmed  milk  (liter) 

Margarine 

Fresh  meat  . 

Salt  pork 

Salt  fish  .... 

Salt 

Pepper    .... 
Tubers    .... 
Vegetables    . 
Bread      .... 

Total       .      . 
Per  day  . 


450. 
275. 
315. 
210. 
630. 

3. 

4. 
185. 
340. 
255. 
250. 
139. 

1. 

200. 

500. 

4760. 


51.8 
33.0 


36. 
27. 

144. 
41. 

159. 
1 

57.8 
28.1 
30.0 


2.4 

0.8 

366.5 


9.0 
4.1 
4.7 

12.6 

12.0 
3.2 

31.9 
157.3 

34.0 
140.3 

30.0 


0.4 

0.1 

61.0 


315.0 
198.0 
223.6 
1.38.6 
330.8 
435.2 
227.7 
1.1 


16.0 

4.0 

2222.9 


980.8' 
140.1 


501.5 
71.6 


4112.9 
587.6 


1,588 

985 
1,109 

797 
2,062 
1,985 
1,883 
1,472 

553 
1,420 

402 


79 

21 

11,192 


25,548 
3,650 


FINLAND— PER  WEEK. 


Food. 

Total 
amount, 
grams. 

Protein, 
grams. 

Fat, 
grams. 

Carbo- 
hydrate, 
grams. 

Calories. 

Scotch  barley 

420 

48.3 

6.3 

298.2 

1.479 

Barley  flour 

700 

80.5 

10.5 

497.0 

2,464 

Oatmeal 

220 

28.6 

13.2 

145.2 

835 

Peas  .      . 

280 

64.0 

5.4 

147.0 

914 

Cheese     . 

385 

138.6 

25.0 

23.1 

895 

Butter     . 

60 

0.4 

51.0 

0.4 

478 

Roast  beef 

300 

51.0 

30.0 

490 

Pork 

210 

21.0 

105.0 

1,065 

Suet  .      . 

84 

0.3 

83.2 

775 

Salt  fish  . 

1050 

115.5 

73.5 

1,157 

Potatoes 

1365 

27.3 

2.1 

285.6 

1,302 

Cabbage 

90 

1.2 

0.3 

7.2 

39 

Syrup 

40 

0.4 

29.6 

124 

Bread 

3990 

459.9 

74.9 

2809.8 

14,105 

Total 

1037.0 

480.4 

4242.7 

26,122 

Per  day 

148.1 

68.6 

606.1 

3.732 

It  is  interesting  to  note  in  the  two  series  of  observations  that  the 
peoples  in  both  countries  derived  the  larger  part  of  their  protein  from 
the  vegetable  kingdom,   only  a  small  amount  coming  from  meat, 


388  CHEMISTRY  OF  FOOD  AND  NUTRITION 

though  in  Finland  a  relatively  large  proportion  of  protein  came  from 
cheese  and  from  salt  fish.  The  chief  source  of  protein,  however,  in 
both  countries  in  these  observations  was  bread.  Again,  it  is  to  be 
observed  that  the  daily  protein  consumption  per  individual  was  high, 
140  to  148  grams.  The  daily  fuel  value  was  likewise  high,  3650  calor- 
ies and  3732  calories. 

By  observations  such  as  these,  made  in  many  countries  and  under 
different  conditions  of  life,  work,  etc.,  so-called  dietary  standards  have 
been  adopted.  These  standards  are  more  or  less  generally  assumed  to 
represent  the  requirements  of  the  body  for  food.  In  Sweden,  laborers 
doing  hard  work  were  found  by  some  observers  to  consume  daily  on  an 
average  189  grams  of  protein,  714  grams  of  carbohydrate,  and  llO  grams 
of  fat,  with  a  total  fuel  value  for  the  day's  ration  of  4726  calories. 
In  France,  it  is  stated  by  a  prominent  physiologist  that  the  ordinary 
laborer  working  eight  hours  a  day  must  have  135  grams  of  protein, 
700  grams  of  carbohyrate,  and  90  grams  of  fat  daily,  with  a  fuel  value 
of  4260  calories.  In  England,  weavers  were  found  to  consume  daily 
151  grams  of  protein,  with  carbohydrate  and  fat  sufficient  to  make  the 
total  fuel  value  of  the  day's  ration  equal  3475  calories.  Observations 
of  this  character,  which  might  be  multiplied  indefinitely,  may  suffice 
to  give  an  idea  of  the  average  food  consumption  of  European  peoples 
doing  a  moderate  amount  of  work. 

In  our  own  country  very  extensive  observations  have  been  made, 
especially  by  the  office  of  the  experiment  station  in  the  Department 
of  Agriculture,  under  the  leadership  of  the  late  Professor  Atwater. 
For  a  period  of  ten  years,  from  1894  to  1904,  dietary  studies  of  the 
actual  food  consumption  of  people  of  different  classes  in  different  parts 
of  the  United  States  were  made  on  about  15,000  persons — men,  women, 
and  children — as  a  result  of  which  certain  standards  have  been 
adopted,  indicating  the  so-called  food  requirements  of  persons  under 
different  conditions  of  life  and  work.  These  standards  vary  from  100 
to  175  grams  of  protein  per  day,  with  a  total  fuel  value  ranging  from 
2700  to  5500  calories.  Some  of  the  foregoing  statements  are  brought 
together,  in  tabulated  form,  in  the  following  table: 


Subjects. 
Swedi.sh  laborers,  at  hard  work  . 
Russian  workmen,  moderate  work 
German  soldiers,  active  service  . 
Italian  laborers,  moderate  work 
French  laborers,  eight  hours'  work 

English  weavers 

Austrian  farm  laborers 


American  subjects. 
Man  with  very  hard  muscular  work 

Man  with  hard  muscular  work 150 

Man  with  moderately  active  muscular  work 
Man  with  light  to  moderate  muscular  work 
Man  at  "sedentary"  or  woman  wilh  moder- 
ately active  work 100  2700 


Protein 

consumed 

daily, 

grams. 

Total  fuel 
value  of 

daily  food, 
calories. 

189 

4726 

132 

3675 

145 

3574 

115 

3655 

135 

4260 

151 

3475 

159 

5096 

175 

5500 

150 

4150 

125 

3400 

.      112 

3050 

CHEMISTRY  OF  FOOD  AND  NUTRITION  389 

These  figures  by  no  means  represent  the  maximum  food  consump- 
tion. Thus,  with  hnnbermen  in  the  Maine  woods,  it  was  found  by 
the  United  States  Dejjartment  of  Agricultiu'e  that  the  intake  of  pro- 
tein food  averaged  185  grams  per  day,  per  in(U\'i(hial,  with  a  total 
fuel  value  of  6400  calories.  The  tendency  has  been  to  assume  that 
figures  such  as  the  above,  which  are  merely  an  expression  of  the  dietetic 
habits  of  people,  show  the  actual  food  requirements  of  persons  under 
difi'erent  coiKlitions  of  life  and  work.  This,  however,  is  an  assumption 
which,  while  it  has  met  with  more  or  less  general  acceptance,  may  be 
questioned  as  being  strictly  logical.  Such  data  are  indeed  interesting 
and  important  as  giving  information  regarding  dietary  customs  and 
habits,  but  there  seems  to  be  no  logical  reason  for  assuming  that  such 
data  represent  the  actual  food  requirements  of  the  body.  As  stated 
by  another:  "Food  should  be  ingested  in  just  the  proper  amount  to 
repair  the  waste  of  the  body ;  to  furnish  it  with  the  energy  it  needs  for 
work  and  warmth;  to  maintain  it  in  vigor;  and,  in  the  case  of  immature 
animals,  to  provide  the  proper  excess  for  normal  growth,  in  order  to 
be  of  the  most  advantage  to  the  body."  Other  physiologists,  like  Voit, 
have  clearly  emphasized  the  general  principle  that  the  smallest  amount 
of  protein,  with  non-nitrogenous  food  added,  that  will  suffice  to  keep 
the  body  in  a  state  of  continual  vigor,  is  the  ideal  diet.  Any  habitual 
excess  of  food  over  and  above  what  is  really  needed  to  meet  the  actual 
wants  of  the  body  is  not  only  uneconomical,  but  may  be  distinctly 
disadvantageous.  Mankind  has  always  been  guided  in  dietary  matters 
by  appetite;  that  is,  by  a  conscious  desire  for  food  and  the  desire 
for  special  kinds  of  food.  But  man  is  a  creature  of  habits;  he  is  quick 
to  acquire  new  ones,  and  he  is  prone  to  cling  to  old  ones  when  they 
minister  to  his  sense  of  taste.  Yet  everyone  knows  that  it  is  quite 
easy  to  acquire  new  habits  in  matters  of  diet  as  in  other  things,  and  it 
is  difficult  for  the  physiologist  to  see  how  habits  and  cravings  can 
constitute  reliable  indices  of  true  physiological  requirements. 

There  would  seem  to  be  no  reason  why  physiological  experiment 
cannot  be  applied  to  a  study  of  this  general  question  of  the  true  food 
requirements  of  the  individual.  This  is  especially  true  of  the  pro- 
tein requirement,  since  it  is  plain,  from  what  has  been  stated,  that 
variations  in  activity,  work  performed,  and  matters  of  that  kind,  do 
not  call  for  material  increase  in  the  intake  of  protein  food  as  it  does  in 
the  consumption  of  non-nitrogenous  foods.  The  very  way  in  which 
protein  foods  behave  in  the  body  makes  one  question  the  necessity  or 
desirability  of  their  excessive  consumption.  The  fact  that  nitrogen 
equilibrium  can  be  established  with  a  relatively  low  nitrogen  intake 
and  that  the  eating  of  larger  amounts  of  protein  food  is  followed  by  a 
corresponding  increase  in  nitrogen  excretion  renders  one  skeptical  of 
the  real  value  of  this  larger  intake  of  nitrogenous  food.  If  protein 
food — in  the  larger  amounts — is  so  important  for  the  body,  why  should 
there  be  such  rapid  decomposition  and  excretion  of  the  larger  part  of 
the  contained  nitrogen? 


390  CHEMISTRY  OF  FOOD  AND  NUTRITION 

Careful  observations  have  been  made  upon  fasting  people,  in 
some  cases  where  fasting  has  continued  as  long  as  thirty  days,  the 
income  being  solely  water.  In  three  somewhat  notable  cases  the  daily 
excretion  of  nitrogen  through  the  urine  was  determined  and  recorded. 
Such  data  are  shown  in  the  accompanying  table,  in  the  cases  of  Breit- 
haupt,  Cetti,  and  Succi.  In  Succi's  case  the  daily  average  loss  of 
nitrogen,  from  the  11th  to  15th  day,  was  5.11  grams;  from  the  16th 
to  2()th,  5.3  grams;  from  the  21st  to  25th,  4.7  grams;  and  from  the 
26th  to  30th,  5.3  grams.  A  daily  loss  of  5.3  grams  of  nitrogen  means 
the  burning  up  of  33  grams  of  protein,  or  a  little  more  than  an  ounce. 
It  is  to  be  noted  from  the  table  that  in  all  three  of  these  cases  the 
amount  of  nitrogen  eliminated  on  the  6th  day  was  essentially  the 
same — practically  10  grams.  This  would  mean  the  breaking  down  of 
62.5  grams  of  protein.  Can  we  assume  from  this  that  men  of  the 
body  weight  here  recorded  need  62.5  grams  of  protein  food  per  day 
to  make  good  the  loss?  Obviously,  this  conclusion  would  not  be 
justified.    Much  would  depend  upon  the  condition  of  the  body  tissue, 

NITROGEN   EXCRETION   THROUGH   THE   URINE. 

Breithaupt  Getti  Succi 

Day  of  (59.9  kilos),        (50.5  kilos),        (62.4  kilos), 

fasting.  grams.  grams.  grams. 

0 13.0  13.5  16.2 

1 10.0  13.6  13.8 

2 9.9  12.6  11.0 

3 13.3  13.1  13.9 

4 12.8  12.4  12.8 

5 11.0  10.7  12.8 

6 9.9  10.1  10.1 

7 10.9  9.4 

8 8.9  8.4 

9 10.8  7.8 

10 9.5  6.7 

as  to  the  amount  of  contained  fat  and  carbohydrate.  In  the  complete 
absence  of  food,  the  body  must  necessarily  feed  upon  itself,  and  in 
fasting  the  degree  to  which  protein  is  broken  down  will  depend  upon 
the  amount  of  available  fat  in  the  tissues.  If  the  body  fat  has  been 
largely  used  up,  then  it  is  plain  that  all  the  energy  needs  of  the  body 
must  come  from  the  l)reaking  down  of  protein.  In  other  words,  the 
feeding  of  fat  and  carbohydrate  would  naturally  diminish  the  break- 
ing down  of  protein,  so  that  quite  likely  these  three  subjects  were 
eliminating  more  nitrogen,  i.  e.,  breaking  down  more  protein  in  the 
6th  and  lOth  days  of  fasting,  than  th(>y  would  if  they  were  consuming 
a  certain  proportion  of  fat  and  carbohydrate. 

A  large  number  of  experiments  upon  various  classes  of  peoi)le  in 
my  own  la})oratory,  covering  long  periods  of  time,  have  led  me  to 
believe  that  for  a  man  weighing  70  kilograms,  or  154  pounds,  there 
is  required  daily  60  grains  of  i)rotein  food  to  meet  the  needs  of  the 
body.  These  are  jjerfectly  trustworthy  figures,  with  a  reasonable 
margin  of  safety,  carrying  perfect  assurance  of  being  fully  sufficient 


CHEMISTRY  OF  FOOD  AND  NUTRITION  391 

to  supply  all  the  physiological  demands  of  the  body;  an  amount  equal 
to  j)ra('tic'ally  one-half  the  Voit  standard  for  a  man  of  this  body  weight. 
In  this  connection  we  must  emphasize  the  fact  that  no  general  state- 
ment can  be  made  applicable  to  mankind  in  general,  l)ut  there  must 
be  due  consideration  of  the  size  and  weight  of  the  individual  structure. 
In  other  words,  a  man  of  170  pounds  body  weight  has  more  protein 
tissue  to  nourish  than  a  man  of  130  pounds  body  weight,  assuming 
that  the  difference  in  weight  is  not  due  to  difference  in  adipose  tissue. 
Putting  the  matter  concisely,  1  believe  that  adults  require  daily  0.85 
gram  of  protein  per  kilogram  of  body  weight. 

SIXTY   GRAMS   OF   PROTEIN    ARE    CONTAINED   IN 

Fuel  value, 
calories. 

One-half  pound  fresh  lean  beef,  loin 308 

Nine  hens'  eggs 720 

Four-fifths  pound  sweetbread 660 

Three-fourths  pound  fresh  liver 432 

Seven-eighths  pound  lean  smoked  bacon 1820 

Three-fourths  pound  halibut  steak 423 

One-half  pound  salt  codfish,  boneless 245 

Two  and  one-fifth  pounds  oysters,  solid 506 

One-half  pound  American  pale  cheese 1027 

Four  pounds  whole  milk  (two  quarts) 1300 

Five-sixths  pound  uncooked  oatmeal 1550 

One  and  one-fourth  pounds  shredded  wheat 2125 

One  pound  uncooked  macaroni 1665 

One  and  one-third  pounds  white  wheat  bread 1520 

One  and  one-fourth  pounds  crackers 2381 

One  and  two-thirds  pounds  flaked  rice 2807 

Three-fifths  pound  dried  beans 963 

One  and  seven-eighths  povmds  baked  beans 1125 

One-half  pound  dried  peas 827 

One  and  eleven-twelfths  pounds  potato  chips 5128 

Two-thirds  pound  almonds 2020 

Two-fifths  pound  pine  nuts,  pignolias 1138 

One  and  two-fifths  pounds  peanuts 3584 

Ten  pounds  bananas,  edible  portion 4600 

Ten  pounds  grapes 4500 

Eleven  pounds  lettuce 990 

Fifteen  pounds  prunes 5550 

Thirty-three  pounds  apples 9570 

To  make  quite  clear  just  what  such  a  standard  of  60  grams  of 
protein  food  means,  attention  may  be  called  to  the  above  table,  in 
which  are  given  the  amounts  of  different  kinds  of  foodstuffs  which 
will  yield  60  grams  of  protein,  and  also  the  fuel  value  of  such  quan- 
tities of  the  foods  in  question.  From  this  table  it  is  seen  that  the  daily 
protein  requirement  of  60  grams  can  be  obtained  from  one-half  pound 
of  uncooked  lean  meat,  from  three-fourths  pound  of  halibut,  from  one 
pound  of  uncooked  macaroni,  from  five-sixths  pound  of  uncooked 
oatmeal,  or  from  two  quarts  of  milk,  etc.  Plainly,  however,  these 
quantities  of  foods  must  be  reinforced  by  addition  of  non-nitrogenous 
foods,  in  order  to  bring  the  fuel  value  to  the  required  amount.  Lastly, 
it  is  to  be  emphasized  that  no  definite  figure  can  be  given  regarding  the 


392  CHEMISTRY  OF  FOOD  AND  NUTRITION 

amount  of  carbohydrate  and  fat  required  in  the  daily  diet,  or  the  total 
fuel  value,  since  this  is  dependent  upon  the  degree  of  activity  of  the 
body.  In  a  general  way,  it  is  perfectly  clear  that  the  sedentary  indi- 
vidual doing  little  muscular  work  needs  far  less  of  non-nitrogenous 
foods,  than  the  individual  who  is  doing  vigorous  work.  My  own  opin- 
ion is  that  the  average  man  leading  an  ordinary  life,  involving  only 
an  average  amount  of  muscular  activity,  needs  in  his  daily  food  a 
total  fuel  value  of  not  more  than  2800  calories. 

The  importance  of  protein  food  in  the  nutrition  of  the  body  has  been 
repeatedly  emphasized.  Stress  has  been  laid  upon  the  quantity  of 
protein  necessary  to  meet  the  needs  of  the  body,  but  in  addition  it  is 
important  to  recognize  the  existence  of  diflferent  nutritive  values  for 
the  individual  proteins.  In  the  animal  and  vegetable  kingdoms  are 
many  different  forms  of  protein  all  superficially  alike,  but  with  a  cer- 
tain degree  of  individuality.  The  casein  of  milk  is  different  from  the 
albumen  of  the  egg;  the  gliadin  of  wheat  floiu*  differs  from  the  gelatin 
of  connective  tissue;  the  protein  of  nuts  has  a  chemical  nature  differ- 
ent from  that  of  the  cereals;  and  so  we  might  make  comparison  of 
hundreds  of  different  proteins  scattered  throughout  the  animal  and 
vegetable  kingdoms,  all  of  which  are  used  in  some  degree  at  least  as 
foods.  ^Yhile  they  are  superficially  alike,  they  are  distinctly  unlike 
in  their  chemical  structure.  This  difference  in  structure  implies  a 
difference  in  physiological  behavior.  The  blood  of  one  species  of  ani- 
mal, with  its  contained  albumens,  cannot  be  injected  into  the  blood- 
vessels of  another  species  without  causing  harm  or  even  death.  Albu- 
minous substances  which  are  foreign  to  the  blood  of  a  given  species 
may  act  as  a  poison  when  introduced  directly  into  the  circulation. 
We,  as  human  beings,  however,  are  feeding  upon  a  mixed  diet  of  pro- 
teins from  all  sources  and  utilizing  these  different  forms  of  protein  to 
our  own  advantage.  The  domestic  animals  as  sheep  and  cattle,  graz- 
ing side  by  side  in  the  same  pasture,  eat  exactly  the  same  food  under 
the  same  conditions  and  yet  each  species  has  in  its  own  fluids  and  tissue 
proteins  peculiar  to  itself.  This  implies  a  process  of  transformation 
or  synthesis,  by  which  individual  proteins  may  be  transformed  into 
other  quite  different  forms  of  protein. 

Native  proteid 


Protoproteose  Heteroproteose 

1  I 

Deuteroproteose  Deuteroproteose 

I  I 

Peptone  Peptone 

I  I 

Amino-acids  Amino-acids 


CHEMISTRY  OF  FOOD  AND  NUTRITION  393 

Protein  foods,  when  eaten,  are  subjected  to  the  action  of  gastric  and 
pancreatic  digestion,  reinforced  by  such  ferments  or  enzymes  as  are 
present  in  the  intestine,  and  as  a  result  the  native  proteins  are  broken 
down  by  successive  stages  through  proteoses  and  peptones  into  the 
comparatively  simple  bodies  known  as  amino-acids,  by  a  process  per- 
haps analogous  to  the  scheme  here  presented.  As  representing  these 
amino-acids  we  have  relatively  simple  crystalline  nitrogenous  sub- 
stances, such  as  glycocoll,  leucine,  proline,  tyrosine,  arginine,  lysine, 
tryptophane,  etc. 

It  is  apparently  with  thesq  amino-acids  that  the  body  has  to  deal  in 
the  construction  of  its  own  tissue  proteins.  These  amino-acids  are 
recombined  by  processes  of  selection  through  synthesis  to  form  organ- 
ized proteins  of  the  kind  characterizing  the  different  tissues  of  the  body. 
Just  how  this  synthetical  construction  is  effected  we  do  not  know,  but 
it  is  assumed  that  the  several  amino-acids  are  combined  one  with 
another,  thus  gradually  building  up  the  complex  protein  molecule. 
Probably  such  amino-acids  as  are  not  needed  to  make  the  required 
proteins  are  burned  up  to  supply  energy.  The  fundamental  idea, 
therefore,  is  that  from  the  supply  of  amino-acids  furnished  to  the  body 
by  the  digested  food  proteins,  the  ones  needed  are  selected  to  construct 
the  particular  tissue  proteins  of  the  animal,  so  far  as  these  are  required 
for  growth  or  tissue  repair.  The  other  point  necessary  to  be  emphasized 
from  the  standpoint  of  nutrition,  especially  with  reference  to  food 
values,  is  that  the  individual  proteins  are  chemically  unlike,  and  con- 
sequently have  different  nutritive  values. 

In  the  laboratory  it  is  possible  to  break  down  protein  artificially 
through  hydrolysis  with  boiling  acids,  in  which  case  the  molecule  is 
broken  apart  into  its  component  amino-acids.  These  can  be  separated 
and  the  amounts  determined.  In  the  following  table  the  composition 
of  eight  distinct  proteins  is  given,  showing  the  percentages  of  amino- 
acids  contained  in  them.  A  study  of  this  table  shows  at  once  what  a 
striking  difference  there  is  in  the  chemical  nature  of  these  individual 
proteins.  Casein  of  milk,  for  example,  as  contrasted  with  the  gelatin 
of  bone,  contains  no  glycocoll,  while  the  latter  contains  16.5  per  cent,  of 
this  substance.  Casein  contains  10.5  per  cent,  of  leucine,  while  gelatin 
contains  2.1  per  cent.  Casein  has  in  it  11  per  cent,  of  glutaminic 
acid,  while  gelatin  has  less  than  1  per  cent,  of  this  amino-acid.  Casein 
contains  tryptophane,  while  gelatin  has  none  of  this  substance.  Again, 
contrast  casein  with  its  1 1  per  cent,  of  glutaminic  acid  with  the  vege- 
table products  hordein  of  barley  and  gliadin  of  wheat,  both  of  which 
contain  over  35  per  cent,  of  this  particular  amino-acid.  These  eight 
examples  are  merely  illustrations  of  the  differences  which  exist  in  the 
chemical  natiu-e  of  the  individual  proteins,  and  since  physiological 
behavior  depends  in  large  measure  upon  chemical  constitution,  it  is 
quite  apparent  that  the  individual  proteins  must  possess  different 
nutritive  values. 


394 


CHEMISTRY  OF  FOOD  AND  NUTRITION 


Aniino-acids. 

g 

.0 
a 

S 
c 

0 

3 
a 

0 

0 

II 

0 

Hi 

GlycocoU 

16.5 

0 

0.6 

0 

0.55 

0 

0.89 

0.94 

Alanine    . 

0.8 

0.9 

2.33 

0.43 

1.8 

2.0 

4.65 

4.45 

Valine 

1.0 

1.0 

1.51 

0.13 

1.04 

0.21 

0.24 

0.18 

Leucine    . 

2.1 

10.5 

8.7 

5.67 

9.65 

5.61 

5.95 

11.34 

Proline 

5.2 

3.1 

3.65 

13.73 

2.77 

7.06 

4.23 

3.18 

Phenylalanine 

0.4 

3.2 

3.55 

5.03 

3.25 

2.35 

1.97 

3.83 

Aspartic  acid 

0.56 

1.2 

3.85 

+ 

5.24 

0.58 

0.91 

3.35 

Glutaminic  acid 

0.88 

11.0 

12.94 

36.35 

14.54 

37.33 

23.42 

6.73 

Serine 

0.4 

0.23 

0 

0.38 

0.13 

0.74 

Tyrosine 

0 

4.5 

3.03 

1.67 

2.18 

1.2 

4.25 

3.34 

Arginine 

7.62 

4.84 

16.02 

2.16 

4.89 

3.16 

4.72 

5.94 

Histidine 

0.40 

2.59 

1.47 

1.28 

1.97 

0.61 

1.76 

2.83 

Lysine 

2.75 

5.8 

1.64 

0 

3.92 

0 

1.92 

2.75 

Ammonia 

1.8 

4.87 

2.06 

5.11 

4.01 

1.41 

Tryptophane 

0 

1.5 

+ 

+ 

+ 

+ 

+ 

+ 

Cj'stine    . 

0.06 

0 

+ 

0.45 

0.02 

38.61 

50.42 

61.09 

71.32 

54.27 

65.81 

59.66 

50.32 

Feeding  experiments  made  upon  animals  have  shown  that  certain 
proteins  contain  all  the  amino-acids  necessary  for  maintenance  and 
growth;  such  proteins  are  frequently  spoken  of  as  ''adequate"  proteins. 
Others  suffice  for  maintenance;  that  is  to  say,  they  furnish  material 
for  the  energy  needs  of  the  body  and  for  the  repair  of  tissue  waste, 
so  that  an  animal  fed  upon  such  proteins  does  not  lose  body  weight, 
but  they  are  quite  inadequate  for  the  purposes  of  growth  in  young 
animals.  Lastly,  there  are  still  other  proteins  which,  when  fed  as  the 
sole  protein  food,  are  insufficient  both  for  maintenance  and  for 
growth;  such  proteins  are  frequently  designated  as  "inadequate" 
proteins.  Gelatin  is  a  good  illustration  of  a  protein  of  the  latter  type. 
It  is  readily  digested  and  ultimately  undergoes  oxidation  in  the  body, 
its  energy  being  utilized;  but  owing  to  its  lack  of  certain  amino-acids, 
such  as  tryptophane  and  tyrosine,  it  is  quite  incompetent  to  maintain 
life;  it  is  not  able  to  maintain  nitrogen  equilibrium;  it  is  not  able  to 
supply  the  nitrogenous  material  needed  for  the  repair  of  the  tissues  of 
the  body.  If,  however,  an  animal  is  fed  upon  a  diet  in  which  gelatin 
is  the  only  protein  substance,  it  can  be  kept  alive  by  adding  trypto- 
phane, cystine  and  tyrosine,  showing  that  these  amino-acids  which 
are  lacking  in  the  gelatin  molecule  are  necessary  for  the  construction 
of  the  i>roteins  needed  b}'  the  animal  system.  In  other  words,  where 
growth  and  maintenance  are  to  be  accomplished,  the  protein  food  must 
contain  the  needed  amino-acids,  or  building  stones,  from  which  the 
tissue  proteins  are  constructed. 

The  gliadin  oi  wheat  and  rye  is  a  prot(!iu  characterized  by  contain- 
ing a  relatively  large  proportion  of  glutaminic  acid  and  ammonia- 
yielding  groups,  with  an  almost  complete  absence  of  lysine  and  glyco- 


CHEMISTRY  OF  FOOD  AND  NUTRITION  395 

coll,  and  very  small  amounts  of  the  amino-acids,  histidine  and  arginine. 
It  has  therefore  a  very  unique  constitution,  very  different  from  the 
tissue  proteins  of  animals,  as  well  as  from  most  of  the  other  proteins 
which  are  commonly  present  in  the  food  of  man  and  animals.  With 
such  a  peculiar  and  one-sided  protein,  feeding  experiments  were  carried 
out  by  Osborne  and  INIendel  on  white  rats  for  long  periods  of  time  cover- 
ing more  than  500  days.  Using  pure  gliadin  as  the  sole  f(jrm  of  protein 
food,  these  animals  were  maintained  in  apparent  health  and  strength 
throughout  the  long  period  of  the  experiment.  There  was  no  impair- 
ment of  the  capacity  to  produce  healthy  young  and  to  nourish  them, 
one  female  giving  birth  to  a  litter  of  four  at  the  end  of  178  days  on  the 
gliadin  foo(l  mixture.  These  young  rats  were  nourished  satisfactorily 
by  their  mother  during  the  first  month  of  their  existence,  so  far  as  could 
be  judged  by  comparison  of  their  increase  in  weight  with  that  of  nor- 
mally reared  rats.  The  results  of  this  experiment  leave  no  doubt  that 
here  where  there  was  such  a  marked  renewal,  or  new  formation,  of 
body  tissue,  very  large  in  proportion  to  the  original  weight  of  the 
mother  animal,  there  must  have  occurred  a  synthesis  not  only  of  the 
building  stones  or  amino-acids  deficient  in  the  protein  intake,  but 
likewise  of  tissue  and  milk  components  of  great  variety  and  complexity 
which  were  completely  missing  in  the  special  food  intake  that  had 
formed  the  sole  food  of  the  mother  during  several  months. 

There  is  another  side  to  this  experiment,  however,  that  must  not 
be  overlooked,  as  it  is  full  of  significance.  At  the  end  of  thirty  days 
three  of  the  young  rats  were  removed  from  the  mother  and  placed  upon 
diets  of  milk  and  other  foods  more  nearly  approaching  the  normal, 
while  the  fourth  animal  was  allowed  to  remain  in  the  cage  with  the 
mother,  whose  sole  source  of  nutriment  was  the  gliadin  food  mixture. 
The  three  removed  animals  manifested  a  normal  growth  on  their 
new  dietaries,  but  the  fourth  animal,  kept  with  the  mother,  began  to 
evince  a  failure  to  grow  at  about  the  period  (30  days)  when  young  rats 
are  wont  to  depend  upon  extraneous  food  for  nourishment.  In  other 
words,  the  young  animal,  forced  to  depend  upon  the  gliadin  food 
mixture  in  place  of  the  milk  of  its  mother,  showed  a  failure  to  grow 
on  the  diet  upon  which  the  mother  had  not  only  been  maintained,  but 
had  actually  produced  young  and  secreted  milk  sufficient  in  quantity 
and  quality  to  induce  normal  growth  in  her  oft'spring.  Young  rats 
fed  on  a  single  protein  of  a  difi'erent  type,  aptly  termed  an  adequate 
protein,  such  as  the  casein  of  milk,  glutenin  of  wheat,  etc.,  will  show 
steady  growth  up  to  say  300  days,  at  which  age  they  normally  grow 
very  little  more.  A  young  gliadin  rat,  on  the  contrary,  fed  solely  on 
gliadin  as  the  protein  part  of  its  food,  can  be  maintained  for  long  per- 
iods, 500-600  days,  but  there  is  no  growth  to  speak  of.  The  youthful 
appearance  of  animals  thus  maintained  without  growth  corresponds 
in  every  respect,  so  far  as  external  characters  go,  with  the  size  rather 
than  the  age  of  the  animal.  The  power  of  growth  in  these  cases,  how- 
ever, is  not  lost,  but  is  simply  held  in  abeyance.    Thus,  in  one  experi- 


396  CHEMISTRY  OF  FOOD  AND  NUTRITION 

ment,  reported  by  Osborne  and  Mendel,  with  gliadin  as  the  sole  pro- 
tein of  the  diet,  after  270  days  of  stunting,  changing  the  diet  to  milk 
powder  in  place  of  gliadin,  growth  began  at  once  and  continued  up  to 
314  days. 

The  animal  body  can  be  maintained  so  long  as  the  protein  supplied 
is  not  deficient  in  certain  indi\idual  amino-acid  groupings  or  building 
stones,  but  there  is  some  other  factor  involved  when  the  problem 
of  gro\\i:h  is  considered.  Given  a  diet  composed  of  some  pure  protein, 
suitable  in  character,  reinforced  with  fat  and  carbohydrate,  the 
animals  will  grow  up  to  a  certain  point  and  then  for  week  after  week 
they  remain  practically  stationary.  Maintenance  may  be  perfect, 
health  and  strength  seemingly  quite  normal,  but  there  is  no  growth. 
The  diet,  so  far  as  its  content  of  nitrogen  and  fuel  or  energy  value  are 
concerned,  may  be  more  than  adequate.  Increasing  the  volume  of 
the  food,  even  when  fully  eaten  and  digested,  brings  no  result.  The 
animal  remains  stunted.  If  now,  without  any  other  change  in  the  diet, 
a  minute  portion  of  dry  milk  powder,  for  example,  is  added  to  the  food, 
growth  at  once  recommences,  and  this  happens  even  though  the  ani- 
mal has  been  stunted  for  a  relatively  long  time.  The  milk  powder  is 
too  small  in  amount  to  give  any  added  fuel  value,  and  it  may  be  freed 
from  all  traces  of  protein  without  causing  any  loss  in  efSciency.  There 
is  plainly  some  accessory  factor  here  which  is  directly  concerned  in 
the  growth  function. 

This  suggests  that  in  the  nutrition  of  the  body,  certainly  in  growth, 
there  are  factors  involved  which  are  wholly  unrelated  to  energy  supply 
or  to  the  amount  and  character  of  the  protein  intake.  In  a  general 
way,  it  may  be  said  that  the  needs  of  the  body  for  food  are  met  by 
so  many  grams  of  protein  or  nitrogen  per  day  and  so  many  calories  or 
kilogram  degree  units  of  heat.  The  chemical  processes  concerned  in 
nutrition  have  for  their  main  object  the  breaking  down  of  these  com- 
plex materials  of  the  food  into  simpler  fragments,  with  liberation  of 
the  contained  energy;  a  series  of  progressive  chemical  decompositions 
in  which  large  molecules  are  broken  down  into  smaller  ones,  and  these 
in  turn  into  still  smaller  ones,  until  finally  the  ultimate  end-products 
are  reached  which  are  cast  out  of  the  body.  Now,  however,  we  see 
the  necessity  of  giving  some  heed  to  the  character  of  the  protein  intro- 
duced into  the  food  supply,  and  the  necessity  of  recognizing  the 
physiological  distinction  between  growth  and  maintenance  as  two  dis- 
tinct phases  of  nutrition.  Finally,  we  have  forced  upon  us  the  experi- 
mental evidence  that  there  are  certain  accessory  factors  concerned  in 
imtrition,  which  in  the  process  of  growth  at  least  are  of  fundamental 
importance. 

As  Professor  Hopkins,  of  England,  has  recently  written,  it  is  possible 
that  what  is  absent  from  artificial  diets  and  supplied  in  such  addenda 
as  milk  and  tissue  extracts  is  of  the  nature  of  an  organic  complex 
(or  of  complexes)  which  the  animal  body  cannot  synthetize.  IJut  the 
amount  which  seems  sufficient  to  secure  growth  is  so  small,  that  a 


CHEMISTRY  OF  FOOD  AND  NUTRITION  397 

catalytic  or  stinnilatin<j  function  seems  more  likely.  Stinuilation  of 
the  internal  secretions  of  the  thyroid  and  pituitary  glands,  which  are 
believed  on  very  suggestive  evidence  to  play  an  imjjortant  part  in 
growth  processes,  can  be  legitimately  thought  of.  On  the  other  hand, 
the  influence  upon  growing  tissues  may  be  direct. 

Here,  then,  we  have  formulated  an  imi)ortant  principle,  viz.,  that 
growth  in  the  young  animal  is  not  so  much  a  question  of  the  amount 
of  the  food  supply,  as  it  is  of  the  presence  or  absence  of  the  specific 
accessory  factors  which,  directly  or  indirectly,  govern  and  control  the 
process.  Indeed,  I  am  inclined  to  make  the  statement  somewhat 
broader  and  to  say  that  the  processes  of  nutrition,  as  a  whole,  are  in 
large  measure  dependent  for  their  proper  working  upon  the  presence 
of  accessories  which  hitherto  have  gained  little  or  no  recognition.  As 
a  recent  writer  has  said,  "  the  animal  body  is  adjusted  to  live  either  upon 
plant  tissues  or  the  tissues  of  other  animals,  and  these  contain  count- 
less substances  other  than  the  proteins,  carbohydrates  and  fats." 

To  give  force  to  my  argument  and  at  the  same  time  to  introduce 
an  additional  fact,  let  me  refer  briefly  to  the  disease  known  as  beri- 
beri and  other  forms  of  peripheral  neuritis,  as  this  may  also  serve  to 
emphasize  how  small  may  be  the  actual  amount  of  a  specific  substance 
which  determines  proper  physiological  functioning.  Beri-beri,  a  disease 
long  known  in  China,  Japan,  the  Philippines,  and  other  localities  w'here 
rice  constitutes  a  prominent  part  of  the  dietary  of  the  people,  has 
always  been  associated  with  rice,  so  that  for  a  long  time  this  staple 
article  of  food  has  been  considered  as  a  causative  factor  in  this  disease. 
During  recent  years,  how^ever,  many  medical  men  have  claimed  that 
the  connection  between  rice  and  beri-beri  w^as  wholly  an  indirect  one, 
the  low  protein  intake  of  peoples  subsisting  mainly  upon  rice  being 
the  real  cause  of  the  disease,  a  hypothesis  wdiich  seemingly  received 
support  at  the  time  of  the  Japanese-Russian  war.  At  this  period  the 
Japanese  army  and  navy  were  placed  on  a  ration  practically  indenti- 
cal  with  that  of  European  nations,  American  canned  meats  being  the 
main  source  of  the  added  protein.  Strange  to  say,  after  this  increase 
in  nitrogen  intake  beri-beri,  which  up  to  that  time  had  been  widely 
prevalent  throughout  the  navy  particularly,  began  to  w^ane  and  soon 
largely  disappeared.  This  fact  has  been  brought  forward  by  many 
writers  as  proof  of  the  greater  efficiency  of  a  high  protein  intake  and 
conversely  of  the  deleterious  effects  of  a  low  protein  diet  on  the  power 
of  resistance  to  disease.  Today  w^e  may  use  this  incident  as  an  illus- 
tration of  how^  mankind  is  prone  to  err  in  drawing  conclusions  from 
observations,  and  how^  frequently  the  unimportant  is  magnified  and 
made  the  nucleus  of  the  argument,  because  by  chance  it  fits  in  wdth 
preconceived  ideas.  As  a  matter  of  fact,  the  high  or  low  protein  intake 
in  itself  has  no  causal  relation  wdiatever  w'ith  the  disease  known  as 
beri-beri;  the  etiology  of  this  disease  is  to  be  sought  for  in  the  rice  itself. 
As  the  work  of  Eykman  and  others  has  showai,  however,  it  is  not  rice 
in  general  that  causes  beri-beri,  but  rice  that  has  been  prepared  in  a 


398  CHEMISTRY  OF  FOOD  AND  NUTRITION 

certain  way.  It  is  only  the  polished  rice,  i.  e.,  rice  that  has  been  cleaned 
of  its  cuticle  and  outer  layers  by  a  process  of  milling  that  is  harmful. 

It  has  now  been  demonstrated  experimentally  that  beri-beri  in  man 
and  polyneuritis  in  fowls,  when  associated  with  rice  as  a  diet,  are  due 
to  the  removal  of  the  outer  portion  of  the  grain  or  the  pericarp.  Prior 
to  1910  beri-beri  was  very  common  throughout  all  the  pubHc  insti- 
tutions of  the  Philippines;  also  among  the  Philippine  troops  of  the 
United  States  Army.  Since  that  date,  when  an  Executive  Order  was 
issued  by  the  Governor-General  of  the  Philippine  Islands  prohibiting 
the  use  of  polished  rice  in  all  public  civil  institutions,  beri-beri  has 
practically  disappeared. 

The  recent  work  by  Funk  suggests  that  the  essential  ingredient  in  the 
rice  polishing  is  an  organic  base;  a  substance  plainly  of  great  physio- 
logical importance.  A  daily  diet  in  which  polished  rice  is  the  main 
ingredient  may  prove  deleterious  simply  because  it  fails  to  provide 
this  important  accessory  compound  that  resides  in  the  outer  layers  of 
the  rice  berry,  or  which  might  be  supplied  by  certain  other  foods,  such 
as  beans,  meat,  etc.  The  smaller  amount  of  nitrogen  furnished  by 
the  rice  diet  is  merely  an  incident  having  no  connection  whatever 
with  the  cause  of  the  disease.  As  illustrating  the  physiological  impor- 
tance of  little  things  in  diet,  it  is  only  necessary  to  state  that  the  amount 
of  this  organic,  nitrogenous  substance  in  rice  is  probably  not  more 
than  0.1  gram  per  kilogram.  Further,  as  Funk  has  shown,  the  curative 
dose  of  the  active  substance  is  very  small;  a  quantity  which  contains 
only  4  milligrams  of  nitrogen  is  sufficient  to  cure  pigeons  in  which 
polyneuritis  has  been  induced  by  feeding  polished  rice. 

Finally,  let  us  turn  to  another  phase  of  protein  metabolism,  or  more 
particularly  that  form  of  metabolism  which  has  to  do  with  the  produc- 
tion of  uric  acid,  a  substance  which  plays  an  important  part  in  con- 
nection with  diseases,  such  as  some  forms  of  rheumatism,  gout,  etc. 
In  the  tissues  of  the  body,  and  as  common  constituents  of  our  food- 
stuffs, are  certain  so-called  purin  bodies,  such  as  hypoxanthin,  xanthin, 
adenin  and  guanin,  to  which  may  be  added  caff'ein,  thein  and  theo- 
bromine; the  three  latter  occurring  only  in  food.  The  purins  present 
in  the  tissues  of  the  body  exist  there  both  free  and  combined.  In  the 
combined  form  they  are  present  as  parts  of  the  nucleins  and  nucleo- 
proteins  which  are  found  in  the  nuclei  of  all  cells,  and  hence  are  present 
in  all  tissues.  Xanthin  and  hypoxanthin  as  free  bases  are  conspicuous 
in  muscle  tissue  and  in  many  organs  of  the  body,  while  adenin  and 
guanin  are  especially  noteworthy  as  components  of  nucleic  acid,  which 
when  combined  with  protein  forms  the  nucleins  and  nucleoproteins 
so  conspicuous  in  every  tissue  cell.  Guanin  and  adenin  are  amido 
bodies,  and  in  the  metabolic  and  other  changes  which  take  place  in 
the  tissues  both  of  these  bases  lose  their  amido  group  and  are  converted 
into  xanthin  and  hypoxanthin,  each  more  highly  oxidized  than  the 
base  from  which  it  is  derived.  The  xanthin  and  hypoxanthin  thus 
formed,  in  their  further  passage  through  the  organism,  are  in  large 


CHEMISTRY  OF  FOOD  AND  NUTRITION  399 

measure  oxidized  to  uric  acid.  Theobromine,  caffein  and  thein  are 
methyl  purins,  and  when  these  compounds  are  taken  into  the  system 
they  first  lose  their  methyl  groups  and  are  then  transformed  into 
xanthin  and  hypoxanthin,  with  the  possiblity  of  ultimate  conversion 
into  uric  acid. 

So  far  it  has  been  implied  that  the  uric  acid  formed  in  the  body  comes 
from  the  transformation  of  free  and  combined  purins  taken  with  the 
food — exogenous  purins — and  from  the  purins  set  free  in  the  tissues — 
endogenous  purins.  In  the  early  history  of  metabolic  studies  bearing 
on  uric  acid  production — or  more  exactly  uric  acid  excretion  through  the 
urine — it  was  thought  that  the  amount  of  uric  acid  was  dependent 
solely  upon  the  quantity  of  protein  food  eaten.  This,  however,  was 
soon  shown  to  be  incorrect,  for  while  it  was  found  that  on  a  diet  rich  in 
meats  and  kindred  products  there  seemed  to  be  a  relationship  between 
the  output  of  nitrogen  and  uric  acid,  thus  suggesting  that  the  amount 
of  uric  acid  formed  was  directly  dependent  upon  the  extent  of  protein 
metabolism,  it  soon  became  apparent  that  this  relationship  held  good 
only  when  flesh  foods  were  taken.  With  vegetable  foods,  or  with  ani- 
mal foods  such  as  eggs,  milk,  etc.,  where,  as  we  now^  know  purins  are 
almost  wholly  absent,  protein  metabolism  may  be  at  a  very  high  level 
with  a  corresponding  increase  in  the  output  of  urea,  while  the  excretion 
of  uric  acid  remains  relatively  low\  In  other  words,  the  factor  above 
all  others  that  influences  the  output  of  uric  acid  through  the  urine  in 
healthy  subjects  is  the  presence  or  absence  of  free  and  combined  purins 
(nucleins)  in  the  daily  food.  Let  me  quote  a  few  results  bearing  on 
this  point  taken  from  our  own  laboratory  experiments: 

First  subject,  70  kilos  body  weight.  High  protein,  purin-free  diet 
composed  of  9  eggs,  2  quarts  of  milk,  200  grams  of  bread,  and  75  granis 
of  butter.  This  day's  diet  contained  138  grams  of  protein,  191  grams 
of  fat  and  241  grams  of  carbohydrate,  with  a  total  fuel  value  of  3300 
calories.  On  this  diet  the  total  output  of  nitrogen  tlirough  the  urine 
was  20.11  grams,  while  the  output  of  uric  acid  amounted  to  only  333 
milligrams. 

Second  subject,  66.6  kilos  body  weight.  Moderate  protein  diet, 
fairly  rich  in  purins.  The  day's  ration  consisted  of  lamb  chops,  sweet- 
bread rich  in  nucleins,  beefsteak  rich  in  free  purins,  potatoes,  aspara- 
gus, peas,  bread  and  coffee  (containing  caffein).  Total  output  of  nitro- 
gen tlirough  the  urine  amounted  to  16.43  grams,  while  the  output  of 
uric  acid  was  623  milligrams. 

In  these  two  cases  the  point  to  be  emphasized  is  that  the  excretion 
of  uric  acid  is  in  no  sense  proportional  to  the  extent  of  protein  metab- 
olism, to  the  extent  of  nitrogen  excretion,  but  is  governed  primarily 
by  the  amount  of  purins  present  in  the  food.  Thus,  the  second  subject, 
with  sweetbread  and  other  purin-containing  articles  in  his  diet,  excreted 
almost  twice  as  much  uric  acid  as  the  first  subject,  although  the  latter 
showed  a  far  higher  total  nitrogen  output;  i.  e.,  a  higher  level  of  protein 
metabolism  in  harmony  with  the  larger  protein  intake. 


400  CHEMISTRY  OF  FOOD  AND  NUTRITION 

If  the  piirin-contaiiiing  food  is  increased  largely  in  amount,  then  the 
uric  acid  excretion  is  found  to  run  parallel.  Thus,  a  third  subject  fed 
for  a  day  largely  on  shad  roe,  rich  in  nucleins,  excreted  on  that  day 
1.37  grams  of  uric  acid;  the  total  nitrogen  output  through  the  urine 
being  21.1  grams,  only  a  little  more  than  was  excreted  by  the  first 
subject.  The  uric  acid  excretion,  however,  on  the  shad  roe  diet  was 
more  than  four  times  that  of  the  subject  on  the  purin-free  diet. 

Fourth  subject,  74.4  kilos  body  weight.  Without  food  of  any  kind 
for  two  days.  On  the  second  day,  the  excretion  of  total  nitrogen 
through  the  urine  amounted  to  9.5  grams,  while  the  output  of  uric 
acid  was  376  milligrams. 

In  this  case  it  is  to  be  noted  that  the  excretion  of  uric  acid  was 
essentially  the  same  as  that  shown  by  the  first  subject  on  a  high 
protein,  non-purin  diet.  Obviously,  these  figures  for  uric  acid  on  a 
purin-free  diet  and  during  fasting  represent  more  or  less  accurately 
the  amount  of  endogenous  uric  acid,  excreted  during  the  twenty-four 
hours,  from  the  disruption  or  breaking  down  of  the  tissue  nucleins, 
and  other  tissue  components.  To  measure  the  endogenous  uric  acid 
accurately  however,  requires  a  somewhat  different  method,  namely, 
a  procedure  that  excludes  any  disturbance  of  the  general  metabolism 
of  the  body,  such  as  undoubtedly  occurs  during  fasting.  The  best 
method  is  to  determine  the  excretion  while  the  subject  is  living  on  an 
adequate  diet,  but  one  that  is  absolutely  purin-free,  say  a  diet  of 
pure  fats,  carbohydrates  and  eggs.  Potatoes,  white  bread  and  milk, 
however,  contain  only  traces  of  purins,  so  that  they,  too,  may  be  added 
to  the  diet  without  danger.  By  such  forms  of  feeding  experiments  on 
men,  notably  those  by  Burian  and  Schur,  it  has  been  demonstrated 
that  the  endogenous  purin  excretion  varies  considerably  with  different 
individuals.  It  does  not,  however,  vary  with  differences  in  the  char- 
acter of  the  diet,  provided  the  latter  is  purin-free  and  is  adequate 
in  amount. 

Obviously,  whenever  it  is  desired  to  diminish  the  amount  of  uric 
acid  floating  about  in  the  body,  a  diet  mainly  vegetable  in  nature, 
or  one  which  is  free  from  meat  and  other  substances  containing  purins 
(free  or  combined),  should  be  followed.  In  such  cases  only  uric  acid 
of  endogenous  origin  will  be  present. 


CHAPTER  XIV. 
DERMATOLOGY. 

By  GEORGE   M.  MacKEE,  M.D. 

In  the  small  space  that  has  been  allotted  for  the  purpose  of  consider- 
ing the  abnormal  conditions  of  the  skin,  it  will  be  possible  to  touch  only 
upon  the  diseases  and  conditions  that  are  most  important  to  munici- 
pal public  school  nurses  and  dental  hygienists.  For  this  reason  it 
will  be  necessary  to  omit  a  lengthy  discussion  of  the  anatomy,  physiol- 
ogy and  hygiene  of  the  normal  skin,  and  it  will  be  impossible  to  deal 
with  affections  which  for  the  most  part  are  of  cosmetic  importance, 
as  well,  also,  as  the  rarer  forms  of  skin  diseases.  A  general  knowl- 
edge of  the  cause  and  diagnostic  characteristics  of  the  skin  diseases 
most  likely  to  be  encountered  in  school,  dental  and  municipal  work 
is,  however,  of  no  little  importance. 

Anatomy  and  Physiology  of  the  Skin.^  It  should  be  understood  that 
the  skin  consists  of  two  parts — the  outermost,  thin  layer  (epidermis) 
and  the  deep,  thick  layer  (derma).  The  derma  contains  the  blood- 
vessels, the  lymphatic  vessels,  the  sweat  and  oil  glands,  the  nerves 
and  the  hair  bulbs.  It  should  be  remembered  that  such  appendages 
of  the  skin  as  the  hair  and  nails  are  formed  in  the  derma  by  an  invag- 
ination of  the  epidermis.  The  derma  is  a  supporting  structure  and  is 
composed  of  connective  and  elastic  tissues. 

The  epiderinis  is  protective.  It  is  composed  of  several  layers  of 
cells  known  as  epithelial  cells.  They  are  produced  by  a  division  of  the 
cells  of  the  lowermost  layer  and  gradually  force  their  way  to  the  sur- 
face. At  first  they  are  oblong  in  shape,  but  as  they  progress  toward 
the  surface  they  become  flattened  and  of  a  somewhat  horny  consis- 
tence. The  outermost  laj^er  of  cells  is  known  as  the  horny  laj'er.  These 
cells  are  being  constantly  shed  as  new  ones  take  their  place.  The  epi- 
dermis can  reproduce  itself,  so  that  its  destruction  is  not  followed  by 
a  scar.  When  the  derma  is  destroyed,  however,  a  modified  tissue  takes 
its  place.  This  is  poorly  supplied  with  the  usual  structures  found  in 
the  derma,  and  such  tissue  is  known  as  cicatricial  or  scar  tissue. 

Besides  acting  as  a  protective  envelope,  the  skin  has  other  physio- 
logical functions  which  cannot  be  discussed  here.  It  might  be  men- 
tioned, however,  that  it  is  important  as  a  respiratory  and  excretory 
organ.  For  this  reason  it  is  advisable  always  to  keep  the  skin  in  good 
condition. 

1  See  Chapter  I,  Fig.  14. 
26 


402  DERMATOLOGY 


ELEMENTARY    NOMENCLATURE. 


Before  entering  into  a  description  of  the  various  skin  diseases  it  will 
be  necessary  to  explain  the  meaning  of  certain  elementary  words  that 
will  be  used  over  and  over  again  in  the  text. 

(a)  Lesion. — A  lesion  means  any  disturbance  in  the  skin.  It  may 
be  a  bruise  (contusion),  a  cut  (incision),  a  raw  spot  (excoriation),  a 
swelling,  an  ulcer,  a  "pimple,"    etc. 

Lesions  are  divided  into: 

Macule. — A  macule  is  a  spot  on  the  skin  that  can  be  seen  but  which 
cannot  be  felt.  It  may  be  of  any  color.  We  usually  limit  the  term  to 
lesions  varying  in  size  from  a  pin-point  or  pin-head  to  a  silver  dollar. 
A  freckle  is  an  example  of  a  macule. 

Papule. — A  papule  is  a  small  solid  lesion  that  can  be  felt  with  the 
finger.  It,  too,  may  be  of  any  color.  Papules  are  the  same  as  macules 
in  size.  They  may  be  flat-topped  or  pointed,  round,  oval  or  square, 
slightly  or  considerably  elevated.  The  small,  hard,  elevation  that 
so  often  follows  a  mosquito  bite  may  be  taken  as  an  example  of  a 
papule. 

Pustule. — A  pustule  is  a  lesion  the  size  of  a  papule,  but  which, 
instead  of  being  solid,  contains  pus.  The  spots  so  frequently  encount- 
ered on  the  face  of  young  people  and  known  as  **  pimples"  are  usually 
pustules. 

Vesicle. — A  vesicle  is  a  lesion,  the  size  of  a  papule,  which  contains 
a  clear  fluid.  Such  lesions  when  larger  than  a  dime  are  called  blebs 
or  bullae  (bulla).  These  three  lesions  are  often  spoken  of  as  blisters. 
While  they  usually  contain  clear  fluid,  the  contents  may  be  cloudy 
and  even  bloody   (hemorrhagic). 

Nodule. — ^A  nodule  is  a  hard  swelling  that  is  too  deep,  or  too  large 
to  be  a  papule.  They  are  usually  about  the  size  of  a  walnut.  They 
may  be  under  the  skin,  so  that  they  cause  very  little  if  any  elevation, 
or  they  may  produce  a  marked  elevation. 

Tumor. — A  tumor  is  really  any  papular  or  nodular  lesion,  but  the 
term  is  usually  employed  to  signify  a  swelling  that  is  larger  than  a 
nodule.    Like  the  nodule,  it  may  be  very  little  or  considerably  elevated. 

(h)  Dermatitis. — This  term  signifies  an  inflammation  of  the  skin. 

(c)  Erythema. — This  is  a  redness  of  the  skin  due  to  a  dilatation  of 
the  blood\'csscis.  The  word  congestion  is  practically  a  synonymous 
term. 

(d)  Edema. — This  is  a  .swelling  of  the  skin  due  to  the  liquid  part 
of  the  blood  (scrum)  passing  out  of  the  vessels  into  the  surrounding 
tissues.  It  is  usually  associated  with  dermatitis,  erythema  or. 
congestion. 

(e)  Circinate  or  Amiular. — These  are  lesions,  usually  papules  or 
macules,  which  assume  the  form  of  a  ring.  They  may  be  produced  by 
a  lesion  clearing  in  the  center  or  by  a  circular  groui)ing  of  individual 
lesions. 


DISEASES  OF   THE  SKIN 


403 


(/)  Gjrrate. — Tliis  term  signifies  an  irregular  outline.  A  gyrate 
patch,  for  instance,  is  formed  by  the  coalescence  of  several  annular 
or  circinate  lesions. 

((/)  Patch  or  Plaque. — These  are  palm-sized,  or  larger,  single  lesions 
or  aggregations  of  indi\idual  lesions. 

DISEASES    OF    THE    SKIN. 

The  first  grou])  of  skin  diseases  to  he  considered  is  that  of  the  para- 
sitir  affcctioN.s.     These  are  divided  into  vegetable  and  animal. 


Fig.  196. — Ringworm. 


Vegetable  Parasitic  Affections. — Ringworm. — Ringworm  of  the  skin 
(Fig.  196)  is  a  very  common  contagious  disease  in  children.  It 
also  frequently  occurs  in  adults.  It  begins  as  a  pin-head-sized,  very 
slightly  elevated,  pale  red,  slightly  scaly  papule.  This  papule  gradually 
increases  in  size  until  it  attains  the  dimensions  of  a  dime,  a  quarter 
or  a  silver  dollar.  As  it  enlarges  it  partially  or  wholly  clears  in  the 
center,  forming  a  circinate  lesion.  In  a  typical  example  the  center 
of  the  lesion  is  composed  of  normal  skin,  while  the  margin  is  slightly 
scaly  and  of  a  pale  red  color.  A  mild  degree  of  itching  is  usually  pres- 
ent. The  lesions  may  be  multi])le;  more  commonly,  howe\'er,  there 
is  but  a  single  ring.  Occasionally  there  is  a  ring  within  a  ring.  It 
may  attack  almost  any  part  of  the  body. 

It  should  be  remembered  that  domestic  animals — cats,  dogs,  and 
cattle — sufl'er   from   ringworm,  and  human   beings   not   infrequently 


404 


DERMATOLOGY 


contract  the  disease  from  contact  with  such  animals.  Fortunately 
the  disease,  excepting  in  the  scalp,  is  not  serious  and  can  be  easily 
cured. 

Ringicorm  of  the  scalp  is  a  much  more  troublesome  malady,  and 
merits  a  separate  description.  Here,  the  disease  not  only  attacks 
the  skin,  but  the  roots  of  the  hair  become  affected,  a  situation  almost 
impossible  to  reach  by  remedial  agents. 

The  symptoms  consist  of  one  or  several  round,  slightly  red,  scaly 
areas  ranging  in  size  from  a  split  pea  to  a  dime  and  even  to  a  silver 
dollar  (Fig.  197).  While  usually  scattered,  they  may  combine  to 
produce  large,  irregularly  shaped  patches.     There  is  usually  a  little 


Fig.  197. — Disseminated  ringworm  of  the  scalp. 


itching.  The  most  typical  feature,  however,  is  the  breaking  of  the 
hair  close  to  the  scalp,  leaving  the  remaining  portion  of  the  hair  appear- 
ing as  a  short  stump. 

A  typical  example  of  ringworm  of  the  scalp  consists  of  a  dime-sized 
patch  of  mild  dermatitis  (redness  and  scaling)  and  hair  stumps.  Occa- 
sionally, the  disease  will  produce  pus  in  the  hair  follicles  and  in  the 
deeper  portions  of  the  scalp.  This  gives  rise  to  a  boggy  swelling,  but 
here,  too,  the  hairs  are  broken  off  close  to  the  scalp.  The  pustular 
form  of  ringworm  of  the  scalp,  after  healing  has  taken  place,  may 
leave  an  area  of  scar  tissue  associated  with  total  baldness,  so  that 
after  an  attack  of  this  kind  it  is  not  uncommon  to  encounter  multiple 


PARASITIC  DISEASES  OF   THE  SKIN 


405 


small  areas  of  baldness.  The  disease  disappears  spontaneously  at 
the  time  of  puberty  and  is  very  rarely  encountered  in  the  adult. 

Animal  Parasitic  Diseases. — Pediculosis. — There  are  three  types  of 
pediculosis,  all  caused  by  a  louse  (pediculus).  The  head  louse  produces 
a  condition  known  as  pediculosis  capitis;  the  body  louse,  pediculosis 
corporis  or  vestimentorum;  and  the  pubic  louse,  pediculosis  pubis. 

Pediculosis  Capitis. — Here,  the  pediculus  inhabits  the  hairy  scalp, 
cementing  its  eggs  (nits)  to  the  shaft  of  the  hair.  The  white  "nits" 
must  be  carefully  differentiated  from  flakes  of  dandruff'.    This  is  easily 


Fig.  198.— Pediculosis. 


accomplished  by  the  fact  that  dandruff  can  be  readily  displaced  from 
the  hairs;  this  is  not  so  with  the  "nits."  The  only  lesions  found  on 
the  scalp  are  scratch-marks,  blood  crusts  and,  occasionally,  pustular 
and  crusted  lesions  which  result  from  infection  following  the  scratch- 
ing,. Itching,  of  course,  is  a  marked  feature.  The  affection  is  encount- 
ered at  all  time  of  life. 

Pediculosis  Corporis  (Fig.  198). — Here,  the  pediculus,  which  is  con- 
siderably larger  than  the  head  louse,  inhabits  the  underclothing.  The 
parasite  itself  produces  no  lesions  upon  the  skin,  but  its  bite  produces 


406 


DERMATOLOGY 


considerable  itching  which,  in  turn,  causes  scratching.  The  scratch- 
ing gives  rise  to  scratch-marks,  excoriations  and  blood  crusts,  with 
occasional  pustules  and  crusted  lesions  from  infection  with  the  ordi- 
nary pus-producing  bacteria.  There  is  probably  no  disease  that  causes 
such  intense  itching  and  such  severe  scratching  as  does  this  affection. 
While  the  entire  covered  part  of  the  body  may  be  affected,  the  lesions 
are  likely  to  be  limited  to  the  areas  that  are  in  close  contact  with  the 
clothing,  such  as  the  upper  back,  the  chest,  the  abdomen  and  the 
buttocks. 

Pediculosis  Pubis. — The  pubic  louse,  while  occasionally  spreading 
to  the  armpits,  chest  and  legs,  usually  is  localized  in  the  genital  region. 


Fig.  199.— Scabies. 


The  insect  is  found  with  its  head  in  a  hair  follicle.  The  egg  is  firmly 
cemented  to  the  hair  close  to  the  skin.  The  only  symptoms  are  the 
severe  itching  and  the  usual  results  of  scratching.  This  affection  is 
limited,  ob\iously,  to  adolescents  and  adults. 

Scabies  (Itch,  Fig.  199). — Scabies,  or  what  is  known  vulgarly 
as  the  itch,  is  a  very  common,  contagious,  animal  parasitic  affection 
in  children  and  adults.  Here,  the  parasite  enhabits  the  skin.  The 
lesions  are  produced  by  the  female  insect,  which  })urrows  along  under 
the  outermost  layer  of  the  skin  and  deposits  her  eggs.  The  first  lesion, 
therefore,  is  a  furrow.  This  is  an  irregular,  fine,  black  line  under  the 
skin.  The  color  is  caused  by  the  excreta  of  the  parasite.  The  insect 
itself  is  too  small  to  be  seen  with  the  naked  ej'e. 


BACTERIAL  DISEASES  OF   THE  SKIN 


407 


The  excreta,  being  a  foreign  body,  ])r()(lu('es  irritation  which  results 
in  the  formation  of  a  vesicle  or  a  pustular  lesion,  usually  the  latter, 
which,  in  a  few  hours  becomes  crusted.  Itching  is  usually  intense 
and  the  skin  shows  evidence  of  scratching.  As  a  rule  the  eruption 
begins  on  the  hands,  especially  between  the  fingers.  It  then  attacks 
the  forearms,  the  armpits,  the  penis  in  the  male  and  the  nipples  in 
the  female.  In  a  severe  case  the  eruj)tion  may  become  quite  general- 
ized.   The  face  and  scalp,  however,  are  never  involved. 

Bacterial  Diseases. — Impetigo  Contagiosa.^ — This  is  probably  the  most 
common  skin  disease  of  childhoo<l.  It  is  also  frequently  observed  in 
adults.  The  affection  is  caused  by  the  ordinary  pus-producing  organ- 
isms   (staphylococcus   and    streptococcus),    and    is   very   contagious. 


Fig.  200. — Impetigo  contagiosa.  The  lesions  are  composed  of  yellowish,  thick, 
porous  crusts  (honey-comb  crusts) .  They  are  easily  removed  on  account  of  the  pus  and 
serum  underneath. 


It  usually  attacks  the  face  and  hands,  but  it  may  occur  on  any  part 
of  the  body. 

The  first  lesion  of  the  disease  is  a  vesicle  which,  in  a  few  horn's, 
becomes  a  pustule.  This  either  ruptures  or  is  broken  and  the  pus  and 
serum  dries  and  forms  a  yellowish-colored  crust.  These  crusts  are 
often  very  thick,  but  porous  and  light  in  weight,  and  are  spoken  of  as 
honey-comb  crusts  (Fig.  200).  It  is  not  common  to  see  the  early 
(vesicular)  stage  of  the  disease.  Usually,  when  the  individual  comes 
under  observation,  there  are  a  few  or  many  small  areas  of  pustular 
or  pustulocrustaceous  lesions. 

The  disease  may  be  primary  or  secondary.  That  is,  it  may  be  con- 
tracted directh'  from  another  individual,  or  it  mav  be  the  result  of 


408 


DERMATOLOGY 


a  discharge  from  the  nose,  eye  or  ear.  Again,  it  may  be  caused  by  infec- 
tion from  scratching,  so  that  the  disease  may  be  secondary  to  such 
affections  as  pediculosis  or  scabies.  When  a  lesion  once  develops  it 
is  likely  to  be  spread  to  other  parts  of  the  body  by  the  hands. 

Acne  (Fig.  201).^ — This  is  the  affection  vulgarly  termed  "pimples." 
It  is  due  to  the  action  of  the  acne  bacillus  together  with  the  staphylo- 
coccus. At  the  age  of  puberty  there  is  a  marked  development  and 
physiological  activity  of  the  oil  (sebaceous)  glands  of  the  face,  which 
appears  to  favor  the  growth  of  the  acne  bacillus.  This  organism,  by 
causing  an  inflammation  of  the  sebaceous  gland  and  duct,  produces 
a  retention  of  the  modified  secretion.  This  plug,  with  its  collection 
of  dead,  black  cells  at  its  outer  end  is  termed  a  comedone  or  "black 
head."  The  pus  organisms  now  become  active  and  a  pustule  is  formed 
around  the  comedone.  It  will  be  obvious  that  this  disease  is  most 
common  at  the  age  of  puberty.    It  may  continue  throughout  the  period 


Fig.  201. — Acne  vulgaris,  showing  pustular  lesions  on  the  face. 


of  adolescence  or  even  into  adult  life.  It  not  infrequently  happens, 
too,  that  the  affection  is  first  manifested  years  after  the  advent  of 
puberty.  It  is  probable  that  the  acne  bacillus  and  staphylococcus  are 
always  present  in  the  skin,  but  they  only  become  active  when  conditions 
favor  their  development.  The  circulation  in  the  so-called  flush  centers 
of  the  face — forehead,  chin,  cheeks  and  nose — can  be  greatly  modified 
by  faulty  gastro-intestinal  conditions  and,  also,  by  lowered  vitality 
of  the  organism  as  a  whole  and  particularly  of  the  nervous  system. 
In  adults,  therefore,  the  indirect  cause  of  the  aft'ection  is  probably  some 
disturbance  in  the  general  health. 

The  disease  may  consist  of  comedones  alone  or  is  associated  with 
papules,  nodules  and  pustules.  The  latter  may  be  small  and  super- 
ficial, or  they  may  be  dee[)-seated  and  as  large  as  a  finger-nail.  There 
is  usually  a  dilatation  of  the  follicles  ("pores")  and  an  excessive  oily 
secretion.     The  disease,  if  allowed  to  exist  for  a  number  of  years, 


DERMATITIS   VENENATA  409 

will  produce  consi(lera})le  scarring  and  will  otherwise  seriously  inter- 
fere with  the  maintenance  of  a  "good  complexion."  While  usually 
limited  to  the  face,  the  affection  may  attack  the  shoulders,  neck,  back 
and  chest.     It  is  not  contagious. 

Boils. — ^These  are  due  to  the  local  and  deep-seated  action  of  the 
staphylococcus.  It  is  not  known  whether  the  infection  is  from  without 
or  within — possibly  both.  In  any  event  an  individual  who  develops 
a  boil  will  usually  have  several  of  them  and  a  "run  of  boils"  is  con- 
sidered as  an  evidence  of  impaired  health.  The  development  of  a 
boil  is  manifested  by  a  stinging  pain  and  the  appearance  of  a  small, 
red  spot,  which  upon  palpation  is  found  to  be  hard.  (It  is  possible  to 
abort  a  boil  in  this  stage  by  the  local  use  of  poultices,  an  incision  and 
other  methods.)  Within  twenty-four  to  forty-eight  hours  a  hard 
nodule  forms  which,  in  a  few  days  softens,  ruptures  and  pus  is  evac- 
uated; healing,  with  scar  formation,  then  occurs. 

A  carbuncle  differs  from  a  boil  in  being  limited  to  one  large  lesion 
with  multiple  pus  pockets. 

Erysipelas. — This  is  a  dangerous  infectious  disease  due  to  a  special 
variety  of  streptococcus.  After  the  organism  enters  the  skin  there 
is  a  diffuse  and  intense  redness  produced,  which  is  accompanied  with 
some  swelling  (edema)  which,  however,  may  be  very  marked  in  cer- 
tain locations,  such  as  the  eyelids.  The  disease  spreads  rapidly  with 
a  sharp  line  of  demarcation,  while  the  parts  first  affected  undergo 
resolution.  The  disease  is  ushered  in  with  a  chill  which  is  followed  by 
a  high  fever.  In  severe  cases  the  patient  may  become  delirious.  The 
germ  gains  entrance  into  the  skin  through  wounds  or  abrasions.  In 
facial  erysipelas  the  portal  of  entry  may  be  the  ear,  or  the  mucous 
membrane  of  the  mouth  or  nose.  Every  case  of  this  disease  should  be 
isolated  as  soon  as  recognized. 

Diseases  due  to  External  Irritants. — ^A  dermatitis  or  inflammation 
of  the  skin,  when  due  to  the  external  application  of  an  irritating  sub- 
stance, is  known  as  dermatitis  venenata.  There  is  a  long  list  of  sub- 
stances that  w^ill  produce  a  dermatitis  venenata  in  susceptible  indi- 
viduals, the  most  common  of  which  are : 

Strong  soap.  -  Varnish. 

Turpentine.  Resinous  woods. 

Metol,  Dyes. 

Primrose.  Sulphur. 

Iodoform.  Chrysarobin. 

Poison  Ivy. 
Most  everyone  is  familiar  with  the  skin  that  has  been  poisoned  with 
one  of  the  poisonous  members  of  the 

Sumac  Family  (Ivy). — The  eruption  is  composed  of  deep-seated 
closely  packed,  minute  vesicles.  This  is  accompanied  with  swelling 
or  edema,  w^hich  may  be  very  severe  around  the  eyes  and  ears.  Occa- 
sionally the  vesicles  are  large,  in  some  cases  as  large  as  a  walnut.  There 
are,  also,  redness,  severe  itching  and,  perhaps,  stinging  and  burning. 


410 


DERMATOLOGY 


The  eruption  begins  at  the  point  where  the  skin  came  in  contact  with 
the  plant,  usually  the  hands  (Fig.  202).  It  then  spreads  to  the  arms, 
face,  and,  in  fact,  to  any  part  of  the  bod}'. 

The  affection  is  not  contagious,  but  it  is  auto-inoculable;  that  is, 
if  the  patient  touches  one  of  his  own  lesions  and  then  touches  his  nor- 
mal skin  with  the  same  finger,  a  new  lesion  will  develop,  but  the  dis- 
ease cannot  be  transferred  from  one  individual  to  another. 


Fig.  202. — Poison  ivy  dermatitis.     Eruption  is  vesicular.     The  skin  is  swollen  and 
red.     Itching  is  severe.     Note  the  large  blister  at  base  of  thumb. 


As  is  well  known,  some  individuals  arc  very  susceptible  to  the  poison- 
ous action  of  ivy,  while  others  are  absolutely  immune.  As  a  rule  it  is 
necessary  to  actually  touch  some  portion  of  the  plant  to  acquire  the 
disease,  but  it  is  possible  that  insects  may  transfer  the  poisonous 
principle  from  the  j)lant  to  the  individual. 

The  aflV'ction  is  not  serious  and  lasts  but  a  few  days,  as  a  rule,  but 
it  may  ccnnpletely  incai)acitate  a  very  susceptible  individual  for  a 
week  or  two.  For  this  reason  every  nurse  and  school-teacher  should 
l)e  acquainted  with  the  ivy  ])laiit  and  should  transfer  this  knowledge 
to  school  children. 


THE  ERYTHEMATA  411 

The  common  i)oison  ivy  is  a  vine  which  may  creep  along  the  fjroimd 
or  cover  walls  and  trees.  At  times  the  growth  of  the  })lant  is  so  vigorous 
that  it  forms  a  bush.  The  main  ])()ints,  however,  are  the  character  of 
the  leaves,  flowers  and  berries.  The  leaves  are  ternate — that  is,  they 
occur  in  threes,  at  the  end  of  a  stem.  The  flowers  bloom  in  June  and 
July;  they  are  very  small,  yellowish-green  in  color  and  are  in  clusters 
at  the  junction  of  the  stem  with  the  stalk.  In  the  fall,  the  leaves  are 
brilliantly  red  and  the  clusters  of  small  green  berries,  which  have 
replaced  the  flowers,  increase  in  size,  and  assume  a  grayish  color. 

Erythema  Group  of  Skin  Diseases. — It  might  be  mentioned  that 
the  classification  used  here  would  not  pass  the  inspection  of  a  derma- 
tologist. The  various  groups  are  arranged  for  the  sake  of  convenience 
and  the  classification  is  not  in  accord  with  that  found  in  dermatological 
literature  (for  instance,  there  is  a  class  of  skin  diseases  known  as 
inflammations,  which  includes  many  of  the  aflFections  already  described, 
the  present  group,  and  aft'ections  that  will  be  described  under  other 
headings).  It  is  to  be  understood  that  the  diseases  are  being  grouped 
for  convenience  of  description  and  that  no  attempt  is  being  made 
toward  an  accurate  or  scientific  classification. 

Erythema  Multiforme. — In  the  text-books  there  are  a  number  of 
affections  which  are  given  various  titles  according  to  the  clinical  appear- 
ance, but  which  we  will  consider  under  the  heading  of  erythema  multi- 
forme. For  instance,  there  is  a  condition  known  as  toxic  erythema, 
where  there  is  a  difl'use  redness  of  the  entire  body,  even,  perhaps,  of 
the  throat  and  mouth,  and  which  simulates  scarlet  fever.  It  is  due 
either  to  the  ingestion  of  poisonous  material  or  to  the  formation  of 
certain  toxins  in  the  intestines,  which  then  enter  the  blood  and  cause 
a  dilatation  of  the  bloodvessels  of  the  skin  with  consequent  redness. 
It  lasts  for  a  few  days  and  then  subsides,  usually  without,  but  some- 
times with,  slight  desquamation.  It  is  often  associated  with  more  or 
less  fever.  It  can  be  (lift'erentiated  from  scarlet  fever  by  the  fact  that 
the  erythema  develops  over  the  entire  body  within  a  few  hours  of  the 
onset  of  the  trouble  and  there  is  likely  to  be  eviflence  of  biliousness. 
There  are  instances,  however,  especially  during  an  epidemic  of  scarlet 
fever,  when  it  is  practically  impossible  to  dift'erentiate  between  the 
two  aft'ections. 

There  is  another  aft'ection  known  as  erythema  nodosum  which  con- 
sists of  painful,  deep-seated  nodules,  co\'ered  with  a  reddened  skin. 
The  nodules  are  walnut-sized  and  occur  on  the  arms  and  legs.  It  is 
most  common  in  young  people  and  is  supposed  to  be  intimately  con- 
nected with  rheumatism.  It  usually  runs  a  course  of  from  one  to 
three  weeks. 

True  erythema  multiforme,  as  its  name  suggests,  consists  of  lesions 
of  various  kinds.  There  may  be  red  patches  ranging  in  size  from  a  pin- 
head-sized  macule  to  areas  a  foot  or  more  in  diameter.  These  may  be 
perfectly  flat  (macular)  or  they  may  be  elevated  by  edema.  There 
may  be  vesiculation  and  even  bullous  lesions.    The  lesions  may  form 


412 


DERMATOLOGY 


various  fantastic  configurations — complete  rings,  broken  rings,  con- 
necting rings,  lesions  within  lesions,  urticarial  wheals,  etc.  The 
mucous  membranes,  particularly  of  the  mouth,  may  be  involved. 
(Fig.  203.)    The  disease  has  the  same  cause  as  toxic  erythema. 

Urticaria. — ^This  disease  {hives)  is  a  very  familiar  and  equally  annoy- 
ing affection.  The  lesion  itself  consists  of  what  is  known  as  a  wheal. 
This  is  a  papule  which  ranges  in  size  from  a  split  pea  to  a  dime.  In 
severe  cases,  instead  of  individual  papules,  there  may  be  palm-sized 
or  larger  elevated  areas.  These  lesions  develop  suddenly  and  are  at 
first  white,  but  soon  become  pink  or  red.  They  itch  intolerably  and 
scratching  only  makes  them  worse.    They  are  usually  transient,  but 


Fig.  203. — Erythema  multiforme.  Lesions  on  lip  consist  of  swellings,  blisters,  and 
crusts.  The  same  condition  is  in  the  mouth.  On  the  body,  there  are  large  irregular 
patches  of  redness  with  here  and  there  a  blister.  The  lesions  on  the  wrists  and  hands 
are  red  rings  with  a  small  central  blister.  In  such  lesions  there  is  often  a  play  of  colors 
aa  seen  in  a  rainbow. 


may  remain  for  several  weeks  or  months.  At  times  the  skin  may  be  so 
irritable  that  the  slightest  touch  \^'^ll  produce  a  wheal — a  condition 
known  as  dermographism  (Fig.  204).  The  affection  is  often  associated 
with  erythema  multiforme. 

The  cause  of  this  disease  is  usually  some  disorder  of  the  alimentary 
tract.  Often  certain  articles  of  food,  such  as  strawberries  and  shell- 
fish, will  1)0  found  as  directly  responsible  for  the  trouble. 

Miscellaneous  Diseases. — Prickly  Heat. — Miliaria  or  prickly  heat, 
as  it  is  called,  is  a  mild  inflammation  of  the  sweat  glands.  The  disease 
consists  of  a  multitude  of  minute  and  closely  crowded  papules.  The 
affection  is  seen  mostly  on  the  trunk,  l)ut  it  often  attacks  the  arms 
and  legs.     It  is  very  common  in  children,  especially  during  the  hot 


HERPES 


413 


weather.  It  is  usually  associated  with  a  stinging  or  burning  sensation 
and  sometimes  with  itching.  The  treatment  consists  of  frequent  bath- 
ing with  cold  water  and  the  application  of  a  talc  powder.  Sweating 
should  be  avoided. 

Herpes. — The  ordinary  "fever  sores"  or  "fever  blisters"  on  the 
lips  are  good  examples  of  herpes.  The  aflFection  consists  of  one  or 
more  groups  of  small  vesicles,  on  an  erythematous  base,  which  are 
usually  associated  with  considerable  itching;  sometimes  they  are  pain- 


FiG.  204. — Urticaria  (hives).  The  small  lesions  on  lower  part  of  back  are  urticarial 
wheals  which  appear  spontaneously.  Whenever  the  skin  of  this  patient  is  scratched, 
it  becomes  slightly  red  and  swollen.  The  letters  were  produced  by  nibbing  the  dull 
end  of  a  pencil  over  the  skin.  These  lesions  do  not  itch  and  this  condition  is  known  as 
dermographism. 


ful.  The  favorite  locations  are  about  the  mouth  (Fig.  205),  the  eyes, 
and  the  genitals,  but  the  disease  may  affect  almost  any  part  of  the  body. 
It  is  not  a  serious  affection  and  disappears  in  a  few  days  without  treat- 
ment. The  affection  is  due  to  an  irritation  of  the  terminal  nerves — a 
reflex.  When  the  lesions  are  on  the  lips  the  irritation  may  be  in  the 
gastro-intestinal  tract,  or  it  may  be  in  some  faulty  condition  of  the 
teeth.  When  the  lesions  are  near  the  e^^e,  the  eyes  themselves  may  be 
at  fault,  etc.  To  prevent  recurrent  attacks  of  herpes,  therefore,  it  is 
essential  that  the  center  of  irritation  be  detected  and  overcome. 


414 


DERMATOLOGY 


Alopecia. — There  are  several  forms  of  alopecia  {baldness,  or  loss  of 
hair)  but  space  will  allow  of  a  careful  consideration  of  only  one  type. 


Fig.  205. — Herpes  simplex.     This  represents  the  ordinary  fever  blisters  seen  on  the  lips. 


Fig.  206. — Alopecia  areata.     The  lesions  ocfur  suddenly  and  the  hair  falls  out  instead 
of  breaking  off  as  in  ringworm.     There  is  no  redness  nor  scaling. 


NEVI 


415 


Alopecia  Areata  (Fig.  2()(')). — This  is  an  aft'ection  wortliN-  of  careful 
consideration,  because  it  occurs  in  both  children  and  adults,  but  mainly 
because  it  is  so  often  mistaken  for  ringworm  of  the  scalp.  It  consists  of 
one  or  several  dime-  to  dollar-sized  completely  bald  patches.  Without 
any  warning  the  hair  falls  out  in  a  few  hours.  Usually  there  is  at  first 
only  one  patch  and,  iufleed,  there  may  be  no  others.  But  not  infre- 
quently, within  the  course  of  a  few  weeks,  several  patches  will  appear. 
There  is  no  redness  or  scaliness  and  no  subjective  symptoms.  Fortu- 
nately, the  hair  usually  grows  again  within  a  few  weeks  or  months, 
although  the  new  hair  may  be  white.  Not  infrequently,  however,  the 
disease  will  denude  the  scalp  and,  in  fact,  the  entire  body,  of  hair.  In 
such  instances  the  hair  rarely  regrows. 


Fig.  207. — Nevus.     This  is  an  example  of  the  common  "port-wine"  birth-mark. 


The  differentiation  from  ringworm  is  easy,  as  all  the  manifestations 
are  quite  the  opposite  from  those  associated  with  ringworm.  Ring- 
worm of  the  scalp  occurs  only  in  children.  The  hair  breaks  off  instead 
of  falling  out.  There  is  a  slow  instead  of  a  sudden  development  and 
there  is  an  erythematous  and  scaly  instead  of  the  smooth  white  skin 
found  in  alopecia  areata. 

Nevi. — Birth-marks  or  nevi  are,  unfortunately,  common  affections. 
The  nevus  most  commonly  seen  is  the  so-called  "port-wine"  mark — a 
dark  red  patch,  usually  seen  on  the  face  (Fig.  207).  (The  best  treat- 
ment for  such  a  birth-mark  is  either  freezing  with  carbon-dioxid  snow 
or  applications  of  the  ultra-violet  ray  by  means  of  the  Kromayer  lamp. 
In  many  instances  this  disfiguring  nevus  can  be  entirely  eradicated.) 
The  condition  is  an  angioma — an  overgrowth  of  the  blood  capillaries 


416 


DERMATOLOGY 


of  the  skin.  When  the  growth  of  vessels  is  under  the  skin,  a  circum- 
scribed, dollar-sized,  red,  soft  tumor  is  produced.  These  tend  to  dis- 
appear as  the  child  grows  older.  Another  type  of  birth-mark  is  the 
pigmented  or  black  nevus,  which  is  usually  associated  with  a  local 
overgrowth  of  hair. 

Adenitis. — Enlarged  lymphatic  glands  (adenitis)  are  caused  by  a 
variety  of  conditions.  Tuberculosis  is  a  common  cause.  Bacterial 
infection  from  the  mouth,  tliroat,  teeth,  ears,  scalp,  etc.,  will  cause 
enlarged  glands  of  the  neck. 

Eczema. — It  is  impossible  to  deal  adequately  in  a  small  space  with 
such  a  complex  subject  as  eczema.  The  affection  is  a  catarrh  of  the 
skin  and  may  be  acute  or  chronic. 


^^H 

^Hf^  ^ 

V 

jI 

^^k^. 

ir"  •     "-  >■  t 

^i- 

-^^" 

^ 

Fig.  208. — Eczema.  This  is  an  example  of  infantile  eczema.  The  skin  is  red  and 
a  little  thickened.  There  is  weeping  and  crusting,  and  considerable  itching.  There  is 
also  pus  formation  under  the  crusts.     Note  the  white  nose  and  lips. 


Acute  eczema  consists  of  circumscribed  patches  or  diffuse  areas  of 
edema  and  redness  with  the  formation  of  vesicles.  It  is  not  unlike 
dermatitis  venenata.  There  is  usually  considerable  burning  or  sting- 
ing. In  severe  examples  the  edema  may  be  a  marked  feature  and 
"weeping"  (exudation  of  serum)  is  noticeable.  In  some  instances 
the  eruption  may  even  become  pustular,  simulating  impetigo. 

Chronic  eczema  (V\g.  208)  usually  occurs  in  patches.  The  skin  is 
thickened,  scaly,  dull  red  and  more  or  less  itchy.  There  may  or  may 
not  be  vesicles.  Chronic  eczema  may  result  from  an  acute  attack  or 
it  may  develop  more  or  less  insidiously.    The  scales  are  dry  and  harsh 


TIJE  INFECTIOUS  EXANTHEMATA  417 

and  are  shed  in  flakes.  The  scaliness  is  not  the  shiny,  micacious  type 
seen  in  psoriasis.  Occasionally,  the  skin  becomes  so  thick  and  hard 
that  painful  fissures  develop.  This  is  seen  especially  on  the  hands. 
A  characteristic  feature  of  eczema  is  that  the  patches  do  not  have,  as 
a  rule,  sharply  defined  margins,  but  gradually  fade  away  into  normal  skin. 

It  should  be  understood  that  there  is  no  sharp  line  of  demarcation 
between  a  dermatitis  and  an  eczema.  As  has  been  mentioned,  an 
erythema  is  a  redness  of  the  skin — a  flushing.  It  is  simply  an  increased 
amount  of  blood  in  the  skin  and  may  be  due  to  many  causes.  Let  us 
assume  that  a  mild,  irritating  substance  is  applied  to  the  skin  and  it 
produces  a  transient  erythema.  Now,  if  this  irritation  is  continued, 
the  erythema  ceases  to  be  temporary,  there  is  a  congestion  and  serum 
and  white  blood  cells  pass  from  the  vessels  into  the  connective  tissues. 
In  other  words,  there  is  an  inflammation — a  dermatitis.  These  con- 
ditions are  well  demonstrated  in  dermatitis  venenata.  Now,  if  the 
inflammation  continues,  all  the  elements  of  the  skin  increase  numer- 
ically, so  that  the  skin  becomes  thickened;  the  outpouring  of  serum,  if 
the  horny  layer  is  intact,  causes  the  formation  of  vesicles  or,  if  the 
horny  layer  is  absent,  a  "weeping."  This  is  catarrh  of  the  skin  or 
eczema. 

Ebzema,  then,  is  simply  a  reactio7i  of  the  skin  to  an  irritant.  This 
irritant  may  be  applied  from  without  or  it  may  be  some  poisonous 
substance  circulating  in  the  blood  and  which  has  been  produced  by 
faulty  metabolism.  Primary  eczema  is  from  the  latter  cause,  while 
secondary  eczema  is  a  sequel  to  various  forms  of  dermatitis,  such 
as  dermatitis  venenata,  scabies,  pediculosis,  etc. 

The  Infectious  Exanthemata. — The  infectious  exanthemata  are  acute, 
febrile,  infectious,  self-limited  conditions,  associated  with  eruptions  of 
the  skin.     We  will  consider  only  the  more  common  of  these  affections. 

Scarlet  Fever. — ^The  onset  of  scarlet  fever  is  sudden.  After  an  incu- 
bation period  of  from  3  to  7  days,  the  disease  is  ushered  in  with  indis- 
position, fever,  headache,  vomiting  and  sore  throat.  The  tempera- 
rises  rapidly  to  from  101°  F.  to  104°  F.;  it  remains  high  until  the 
eruption  is  fully  developed,  when  it  gradually  declines.  The  tongue  is 
coated  and  shows  numerous  red  spots — the  "strawberry  tongue." 

The  rash  appears  on  the  second  day  and  is  first  seen  on  the  neck.  It 
then  rapidly  spreads  to  the  face,  chest,  arms,  legs,  etc.  It  reaches 
its  maximum  of  development  about  the  fourth  day  and  then  gradually 
fades.    This  is  followed  by  desquamation  of  the  skin. 

The  eruption  consists  of  a  bright  red  flush  with  closely  crowded 
puncta  (pin-point  elevations).  The  disease  is  said  to  be  infectious 
for  three  weeks,  so  the  patient  must  be  isolated  for  this  period.  The 
afl^ection  varies  markedly  in  severity,  but  it  is  always  dangerous. 
Severe  complications  and  sequelae  are  common,  such  as  aft'ections  of 
the  eye,  ear  and  brain. 

Measles. — After  an  incubation  period  of  about  10  days,  the  individual 
develops  a  "cold" — an  inflammation  of  the  nose,  eyes  and  throat. 
27 


418  DERMATOLOGY 

The  temperature  rises  to  101°  F.  to  103°  F.  After  about  four  days 
small  red  spots  with  a  minute  bluish-white  center  can  be  detected  on 
the  mucous  membrane  of  the  cheeks.  About  this  time  the  eruplion 
begins  on  the  neck  and  face  and  gradually  spreads  downward  over  the 
entire  body.  The  eruption  consists  of  red  macules  which  range  in 
size  from  a  pin-head  to  a  bean  or  finger-nail  and  are  irregular  in  outline. 
After  the  disappearance  of  the  eruption  there  is  a  slight  desquamation. 
An  uncomplicatefl  case  runs  a  course  of  from  7  to  14  days. 

^Measles  is  not  in  itself  very  dangerous.  The  most  common  compli- 
cation of  the  disease  is  pneumonia — an  affection  with  a  high  mortality. 

German  measles  is  hardly  anything  more  than  a  very  mild  case  of 
ordinary  measles. 

Chicken-pox. — Chicken-pox  is  not  a  serious  disease.  After  an  incuba- 
tion period  of  from  14  to  17  days,  an  eruption  of  umbilicated  vesicles 
occurs  on  the  neck  and  face  and  then  over  the  entire  body.  The 
vesicles  develop  in  crops  about  12  to  24  hours  apart,  so  that  there  are 
always  lesions  in  various  stages  of  evolution.  After  a  few  hours  the 
contents  of  the  vesicles  become  cloudy  and  in  a  few  days  they  dry  up 
and  disappear.  Occasionally  a  scar  is  produced.  There  is  usually 
some  itching.  There  is  not  much  fever.  The  disease  lasts  about  a 
week  or  ten  days. 

Syphilis. — This  disease  may  be  considered  as  the  most  important 
of  all  the  diseases  in  dermatology.  It  is  an  afl'ection  which  attacks 
individuals  of  all  ages;  a  disease  that  can  be  passed  from  a  mother  to 
her  unborn  infant;  a  disease  that  is  highly  contagious  and  one  that 
will  produce  the  most  horrible  results  if  neglected  or  improperly 
treated. 

The  increase  in  our  knowledge  of  syphilis  has  been  so  great  in  the 
last  few  years  that  it  will  be  worth  while  to  outline  the  history  of  the 
disease. 

History. — Syphilis  became  known  to  the  civilized  world  in  1494. 
It  first  appeared  in  Spain  upon  the  return  of  Columbus  and  his  crews. 
There  is  no  record  of  the  disease  having  existed,  prior  to  this  time, 
in  any  civilized  country,  but  there  is  plenty  of  evidence  regarding  the 
existence  of  the  afi'ection  in  Central  America,  previous  to  the  voyages 
of  Columbus.  After  its  first  appearance  in  Europe,  the  disease  spread 
rapidly  throughout  the  entire  world,  attacking  people  of  all  classes. 
The  disease  then  was  much  worse  than  it  is  now.  This  was  because 
there  was  at  first  no  adequate  method  of  treatment  and,  also,  because 
the  aftection  was  working  on  virgin  soil — that  is,  it  was  destroying 
the  most  susceptible  subjects  and  leaving  the  more  or  less  immune 
individuals  to  ])roduce  i)rogeny  who  were  less  susce])tible.  The  ravages 
of  the  disease  in  the  loth  and  Kith  centuries  almost  <lefy  description. 

No  disease  has  ever  been  so  carefully  studied  as  sy])hilis  and,  although 
a  good  clinical  knowledge  was  acquired  and  efficacious  methods  of 
treatment  were  (l('vcl()j)ed,  it  was  not  until  about  1895  that  we  accumu- 
Uitcd  definite  scientific  facts  of  great  importance.    About  this  time  there 


SYPHILIS  419 

occurred  a  clniiu  of  events  well  worth  mentioning  and  wliich  succeeded 
in  replacing  mystery  by  definite  scientific  know-ledge. 

Previous  to  1895  Ricord,  Fournier,  Xeisser  and  many  other  scien- 
tists had  given  us  valuable  information,  but  the  first  link  in  the  chain 
of  events  already  mentioned,  was  the  discovery  by  Metchnikoff  and 
Roux  that  the  disease  could  be  ])assed  directly  from  man  to  the  ape. 
Klingmuller  then  demonstrated  that  the  well-filtered  virus  was  harm- 
less. But  it  remained  for  Schoudinn  and  Hoffmann  to  discover  the 
specific  microorganism,  which  they  named  the  Spirorhcta  yallula  or 
Treponema  pallidum.  Recently  Noguchi,  working  in  the  Rockefeller 
Institute  in  New  York,  has  succeeded  in  cultivating  the  organism. 

As  might  be  expected,  the  discovery  of  the  cause  of  the  <lisease  has 
led  to  improved  methods  of  treatment.  To  the  time-honored  mercury, 
has  been  added  the  exceedinglv  valuable  salvarsan  or  "OOC)"  as  it  is 
called. 

Methods  of  Cuntagion. — There  is  a  mistaken  idea  among  the  laity 
that  syphilis  is  acquired  only  by  sexual  contact.  This  erroneous  belief 
has  been  the  cause  of  a  great  deal  of  harm.  The  sooner  syphilis  is 
considered  an  infectious  and  contagious  disease  and  the  sooner  it  is 
looked  upon  in  much  the  same  light  as  is  tuberculosis  and  similar  aft'ec- 
tions,  the  better  will  it  be  for  everyone  concerned.  The  disease  is 
contracted  in  many  w^ays,  of  which  sexual  intercourse  is  but  one 
example.  The  syphilitic  is  likely  to  be  a  constant  source  of  danger 
from  the  standpoint  of  contagion.  He  may  infect  eating  and  drinking 
utensils,  tonsorial  instruments  etc.;  he  may  transmit  the  disease  by 
kissing  or  even  by  shaking  hands.  P'ortunately,  the  Spirocheta  pallida 
lives  but  a  few  hours  outside  of  the  human  body;  otherwise  nearly 
everyone  would  sooner  or  later  contract  the  afl'ection.  The  organism, 
fortunately,  cannot  penetrate  the  unbroken  skin  or  mucous  membrane, 
so  that  an  abrasion  is  necessary,  but  this  abrasion  may  be  so  small, 
so  insignificant,  as  to  pass  unnoticed.  Inoculation  always  takes  place 
either  in  the  skin,  or  in  the  mucous  membrane  of  the  mouth  or  genitals. 
There  are  a  few  exceptions  to  this,  but  they  will  not  be  considered 
here. 

Methods  of  Prevention. — A  syphilitic  can  only  infect  another  indi- 
vidual when  he  has  active  manifestations  of  the  disease  and  then,  as 
a  rule,  only  in  the  early  periods  of  the  afi'ection.  It  is  the  duty  of  the 
physician  to  instruct  the  patient  regarding  the  danger  to  others  and 
to  treat  him  in  such  a  way  as  to  overcome  at  once  all  active  and  con- 
tagious manifestations.  On  account  of  the  possibility  of  transmitting 
the  disease  to  their  oft'spring  syphilitic  individuals  should  not  marry 
until  the  disease  is  cured. 

Dentists  are  in  constant  danger  of  infection,  and  they  should  always 
inspect  the  mouth  for  the  presence  of  suspicious  lesions.  If  present, 
they  should  be  cauterized  and  the  mouth  rinsed  with  an  antiseptic 
solution,  or  rubber  gloves  may  be  employed.  Whenever  a  dentist 
detects  a  w^ound  upon  his  finger  he  should  protect  it  with  collodion. 


420 


DERMATOLOGY 


Instruments  should  be  properly  sterilized  to  prevent  the  carrying  of 
the  infection  from  one  patient  to  another.  If  an  individual  has  reason 
to  suppose  that  inoculation  has  occurred,  the  development  of  the  disease 
may  be  prevented  by  applying  the  following  ointment  within  eight 
hours  of  the  time  of  the  infection: 

IJ — Calomel 160  grains 

Lanoline 320  grains 

This  ointment  must  be  applied  before  the  end  of  eight  hours  and 
should  be  massaged  into  the  area  for  a  period  of  five  minutes.  When 
handling  a  suspicious  case  the  ointment  may  be  rubbed  into  the  hands 
before  operating.  The  saliva  of  a  syphilitic  is  not  contagious  unless 
there  are  lesions  of  early  syphilis  in  the  mouth  or  throat. 


Fig.  209. — Syphilis.  Showing  the  remains  of  a  chancre  of  the  lower  lip.  Note 
the  macular  eruption  on  the  body.  This  is  the  beginning  of  the  secondary  period. 
The  patient  had  not  received  treatment.     Note  the  symmetrical  distribution. 


Description  of  the  Disease. — Stages. — Syphilis  is  divided  into  three 
stages,  namely,  primary,  secondary  and  tertiary. 

Primary  Period. — After  infection  there  is  a  period  of  incubation 
lasting  from  one  to  three  weeks.  Then,  upon  the  site  of  the  inoculation, 
there  appears  a  slow-developing  lesion  known  as  a  chancre  or  initial 
lesion  (Fig.  209).  It  begins  as  a  small  papule  which  slowly  increases 
in  size  until,  at  the  end  of  a  week  or  two,  it  assumes  the  dimensions 
of  a  dime.  It  is  now  considerably  elevated  above  the  surrounding 
surface  and  is  very  hard.  TJie  center  then  becomes  ulcerated.  After 
reaching  its  maximum  of  development,  the  lesion  slowly  involutes 


SYPHILIS  421 

and  disappears  in  a  few  weeks  without  much  scar  formation.  Occasion- 
ally, there  may  be  considerable  ulceration,  or,  rarely,  the  lesion  may 
not  become  an  ulcerated  nodule,  but  remain  as  a  papule.  The  chain  of 
lymphatic  glands  that  drain  the  region  are  afi'ected.  Usually,  there 
is  one  large  gland  in  the  immediate  neighborhood  of  the  chancre; 
this  is  known  as  the  satellite  or  pilot  gland. 

Secondary  Period. — This  period  represents  systemic  involvement. 
The  virus  after  leaving  the  chancre  passes  through  the  lymphatic 
channels  and  enters  the  blood  stream,  by  which  it  becomes  dissem- 
inated throughout  the  body.  Usually  the  first  clinical  evidence  of 
secondary  syphilis  is  the  development  of  a  generalized  adenitis — a 
slight  swelling  of  all  or  nearly  all  of  the  lymphatic  glands  of  the  body. 
This  occurs  from  three  to  twelve  wrecks  after  the  appearance  of  the 
chancre.  A  week  or  two  after  the  occurrence  of  the  lymphatic  involve- 
ment there  is  an  eruption  of  red  macules.  The  individual  lesions  are 
not  scaly,  as  a  rule,  and  range  in  size  from  a  split  pea  to  twice  this  size. 
The  eruption  may  cover  the  entire  body  or  it  may  be  limited  to  cer- 
tain regions,  such  as  the  trunk.  The  macular  eruption  develops  slowly 
and  may  disappear  spontaneously  in  a  few  weeks,  or  the  macules  may 
become  papules  (Fig.  210),  which  may  or  may  not  be  scaly.  Associated 
with  this  cutaneous  eruption  there  are  usually  a  sore  throat  and  lesions 
in  the  mouth  which  are  known  as  mucous  patches  and  which  will  be 
described  in  detail  later.  In  addition  to  the  features  already  men- 
tioned, it  is  extremely  common  to  observe  a  loss  of  hair,  and  this 
alopecia  assumes  a  very  definite  type.  The  hair  falls  out  in  patches, 
but  the  involved  areas  are  never  completely  bald  as  in  alopecia  areata; 
there  are  always  numerous  healthy  hairs  left  in  the  patches,  so  that 
the  scalp  has  a  "moth-eaten"  appearance. 

As  a  rule  the  early  secondary  period  of  the  disease  is  not  associated 
with  severe  symptoms.  There  may  be  slight  fever,  anemia,  sore  throat, 
loss  of  appetite,  etc.  Usually  all  these  symptoms  tend  to  disappear 
spontaneously.  In  many  individuals,  the  secondaries  are  so  slight 
and  so  transient,  as  to  be  unnoticed  and  if,  perchance,  the  chancre 
was  in  the  vagina  or,  if  for  any  other  reason,  was  overlooked,  the 
patient  might  not  be  conscious  of  the  presence  of  syphilis  until  after 
the  lapse  of  many  years,  when  destructive  skin  lesions  or  grave  and 
dangerous  nerve  or  visceral  manifestations  demonstrate  the  presence 
of  the  disease. 

On  the  other  hand,  especially  in  neglected  syphilis,  the  manifes- 
tations of  secondary  syphilis  may  be  very  severe.  The  eruptions  and 
symptoms  already  mentioned,  may  persist  or  if  they  were  transient, 
they  are  likely  to  return  and  produce  what  is  known  as  secondary 
relapsing  syphilides.  These  relapsing  syphilides,  which  usually  occur 
in  the  first  year  of  the  disease,  have  certain  definite  characteristics. 
They  are  always  bilateral  and  usually  symmetrical — the  same  lesions 
on  both  sides  of  the  body.  They  are  usually  limited  to  certain  regions, 
such  as  the  hands,  arms,  legs,  trunk,  face,  etc.,  rarely,  although  occa- 


422  DERMATOLOGY 

sionally  becoming  generalized.  The\'  consist  mainly  of  raw-ham- 
colored,  scaly  pai)ules  arranged  in  groups  and  tending  to  produce 
circinate,  annular  and  gyrate  configurations.  It  is  uncommon  to  have 
ulcerative  or  destructive  lesions  in  the  first  year  or  two  of  the  disease. 
This,  however,  occasionally  happens  in  precocious  syphilis. 


Fig.  210. — Sypliili.s.  .\  i-ajjulai-  ciuptiuu  in  I  hi'  sfcoudaiy  period  of  an  untreated 
case.  The  papules  are  of  split-pea  size,  scaly,  and  of  a  raw-ham  color.  Note  the 
symmetrical  distribution. 

In  severe  examples  of  the  disea.se  there  may  be  nocturnal  headache, 
which  denotes  an  involvement  of  the  nervous  system.  In  addition, 
the  optic  or  auditory  nerves  may  be  involved. 

Mucous  Patch. — This  will  })e  given  especial  consideration  on  account 
of  its  interest  to  dentists  and  their  associates.  The  mucous  patch  is 
a  su])crfic'ud  ulcer  ranging  in  size  from  a  split  pea  to  a  finger-nail,  and 
situated,  usiiall>-,  on  the  buccal  mucosa — lii)s,  cheeks,  tongue,  palate 
and  throat.    It  is  covered  with  a  dirty,  grayish-white  mend)rane  which. 


SYPHILIS 


423 


when  removed,  leaves  a  superficial  excoriation.  There  may  he  but  a 
single  patch  or  there  may  be  several  of  them  (Fig.  211).  Another 
lesion  of  interest  to  dentists  is  the  so-called  split  i)ai)ule.  This  is  a 
l)ai)ule  at  the  corner  (connnissure)  of  the  mouth,  and  which  is  j)artly 
in  the  skin  and  partly  in  the  mucous  membrane.  On  account  of  its 
location  it  is  usually  fissured. 

All  the  lesions  of  early  syphilis  are  rich  in  Spirocheta  pallida  and  are 
therefore  conta(/ious.  If,  however,  the  skin  covering  the  lesion  is 
unbroken,  there  is  no  danger  of  contagion.  On  the  other  hand,  all 
moist  lesions  of  early  syphilis,  such  as  the  mucous  patch,  the  chancre, 
the  split  papule,  etc.,  are  extremely  contagious.  The  blood  of  a  syph- 
ilitic patient,  unless  obtained  directly  from  a  lesion,  is  very  slightly 
if  at  all  dangerous.  The  secretion  and  excretions,  such  as  the  saliva, 
need  not  be  considered  dangerous  unless  contaminated  with  the  dis- 
charge from  a  lesion. 


Fig.  211. — Syphilis.     Mucous  patches  in  the  secondary  period  of  an  untreated  case. 
The  patches  in  this  individual  were  of  long  duration  and  had  become  somewhat  warty. 

Tertiary  Period. — There  is  no  sharp  line  of  demarcation  between 
secondary  and  tertiary  syphilis.  In  a  general  way  the  secondary  period 
may  be  considered  to  end  at  the  termination  of  the  second  year.  The 
tertiary  period,  beginning  at  the  end  of  the  second  period,  lasts  through- 
out life,  providing,  of  course,  that  the  disease  has  not  been  cured. 
Manifestations  of  the  tertiary  period  may  develop  early  in  the  period, 
or  the  disease  may  remain  quiescent  for  months  or  even  for  many 
years,  only  to  have  lesions  appear  late  in  life.  Tertiary  syphilis  is 
noted  for  its  destructive  skin  lesions  (Figs.  212  and  213)  and  for  its 
tendency  to  produce  serious  involvement  of  the  internal  organs, 
(viscera)  and  the  nervous  system. 

Tumors  may  develop  in  the  brain  and  produce  pressure  symptoms; 
the  symptoms,  of  course,  depend  upon  the  particular  part  of  the  brain 
that  is  involved.     The  entire  brain  may  become  affected,  producing  a 


424 


DERMATOLOGY 


condition  known  as  paresis.  Certain  portions  of  the  spinal  cord  may 
be  diseased,  resulting  in  a  condition  known  as  locomotor  ataxia. 
The  arterial  system  is  usually  more  or  less  affected,  giving  rise  to 
arteriosclerosis.  In  fact  there  is  hardly  any  part  of  the  organism  that 
may  not  be  attacked  by  tertiary  syphilis. 


Fig.  212. — Syphilis.  An  example  of  an  eruption  composed  of  ulcerating  nodules  in 
neglected  syphilis  of  the  tertiary  period.  Note  the  gyrate  configuration,  also  the  scars 
and  pigmentation. 

In  the  skin,  tertiary  s^^3hilis  is  manifested  by  slow-developing, 
large,  deep-seated  ulcers.  These  ulcers  are  not  infrequently  preceded 
by  deep-seated,  soft  tumors.  Another  type  of  the  tertiary  skin  lesion 
is  a  group  of  deep-seated,  half-dime  to  dime-sized,  raw-ham-colored 
nodules,  which  undergo  ulceration  w^ith  crust  formation. 


Fig.   213.— Syphilis. 


An   example  of  an   ulcerating  deep-seated   tumor    (gumma)    in 
neglected  tertiarj'  syphilis. 


The  points  to  remember  about  tertiary  skin  manifestations  are  that 
the  lesions  tend  to  ulcerate  and  to  produce  scars.  The  color  is  a  dark 
red  or  raw  ham.  There  is  usually  a  marked  pigmentation.  The  lesions 
are,  as  a  rule,  unilateral — on  one  side  of  the  body  only — and  hardly 
ever  symmetrical.  The  disease  at  this  stage  very  frequently  attacks 
the  bones  (Fig.  214), 


SYPHILIS  425 

Instead  of  being  ulcerative  or  gummatous  (tumors)  or  nodular, 
the  lesions  may  be  of  the  squamous  type  (scaly),  especially  on  the 
palmar  surfaces  of  the  hands  and  plantar  surfaces  of  the  feet.  Such 
lesions  resemble  eczema,  but  they  can  be  differentiated  from  this 
disease  because  in  syphilis  the  patches  are  always  sharply  marginated 
and  unilateral.  In  fact  all  syphilitic  lesions  are  sharply  marginated 
and  they  almost  always  tend  to  produce  peculiar  configurations — 
scalloped  edges,  gyrate  and  annular  lesions,  etc.     Another  point  is 


Fig.  214. — This  shows  syphilitic  involvement  of  the  bones  as  seen  in  hereditary  and 
tertiary  syphilis.  The  lesion  consists  of  a  thickening  of  the  periosteum  and  multiple 
abscesses  in  the  bones — a  periostitis  and  an  osteomyelitis. 

that  late  syphilitic  lesions  tend  to  progress  slowly,  while  the  older 
parts  heal — this  is  known  as  a  serpiginous  lesion  and  is  quite  t\'pical 
of  s\T3hilis,  although  such  lesions  do  occur  in  other  rare  skin  affections. 
As  a  rule  the  tertiary  lesions  of  syphilis  are  not  contagious,  or  at  least 
very  slightly  so  and  children  born  during  this  period  may  never  show 
manifestations  of  the  disease. 

Hereditary  and  Congenital  Syphilis. — If  pregnancy  occurs  during  the 
early  secondary  period  of  syphilis  the  disease  is  likely  to  cause  the 


426 


DERMATOLOGY 


death  of  the  fetus.  If,  however,  a  li\'e  infant  is  born,  it  will  usually 
demonstrate  evidence  of  congenital  syphilis  within  a  few  weeks.  The 
manifestations  of  congenital  syphilis  are  a  discharge  from  the  nose 
(snuffles)  a  poorly  nourished  condition,  sores  in  the  mouth  and  an  erup- 
tion of  bullae,  vesicles  or  papules  on  the  body.  Such  infants  usually 
die  within  a  few  months  in  spite  of  treatment.  If  a  child  is  born  in 
the  late  secondary  period,  it  also  may  develop  congenital  manifes- 
tations or  it  may  escape  congenital  syphilis,  only  to  demonstrate  hered- 
itary syphilis  sometime  during  life. 

Hereditary  syphilis  is  manifested  in  various  w^ays.  We  will  mention 
only  the  most  common  types,  any  one  of  which,  or  any  combination 
of  which  may  occur  in  a  given  individual :  Faulty  mental  development 
which  may  range  from  a  slight  "defective"  to  complete  idiocy;  signs 
of  nerve  involvement,  such  as  deafness,  blindness,  etc.;  faulty  physical 
development — stunted  growth,  "box-shaped"  head,  "saddle"  nose 
(bridge  of  nose  concave  instead  of  convex),  Hutchinson's  teeth,  etc. 

Hutchinson's  teeth  represent  one  of  the  most  common  hereditary 
taints.  This  feature  consists  of  a  central  notching  of  the  superior 
central  incisors  (Fig.  215). 


Fig.  215. — Syphilis.  An  example  of  Hutchinson's  teeth  seen  in  untreated  hereditary 
syphilis.  Usually  only  the  upper  permanent  central  incisors  are  centrally  notched. 
Here  both  the  upper  and  lower  central  incisors  have  a  central  notching. 


Besides  the  above  hereditary  manifestations  there  may  be  destruc- 
tive lesions  of  the  skin  and  especially  of  the  bones — as  seen  in  tertiary 
syphilis.  The  symptoms  of  hereditary  syphilis  may  occur  early  in 
life  or  they  may  not  become  manifest  until  the  individual  is  nearly 
twenty  years  of  age. 

The  buccal  lesions  of  late  syphilis  are  of  special  interest  to  the  dentist 
and  his  co-workers.  These  manifestations  may  consist  of  tumors 
(gummataj,  ulcers  (ulcerating  gummata)  or  leukoplakia. 

Gummata. — While  gummata  may  occur  anywhere  in  the  mouth 
or  throat,  the  most  common  site  is  the  dorsal  surface  of  the  tongue 
where  they  usually  form  a  soft,  circumscribed,  oblong,  considerably 
elevated,  painless  tumor,  which,  if  neglected,  tends  to  break  down  and 
produce  an  ulcer.  Ulcerating  gummata  are  also  commonly  found  on  or 
near  the  soft  palate  wliere  the  tendency  is  for  the  disease  to  perforate 
the  roof  of  the  mouth  (Fig.  21(j).  These  same  lesions  may  occur  on 
the  mucous  surfaces  of  the  cheeks,  especially  in  the  neighborhood  of 


SYPHILIS 


427 


the  mouth.  Here,  there  is  more  hkely  to  be  a  rather  diffuse  and 
une^'en  infiltration,  the  mucosa  is  thrown  into  folds  and  there  is  more 
or  less  ulceration. 

Buccal  gummata  must  be  differentiated  from  tuberculosis  and 
cancer.  Both  tul)erculosis  and  cancer  of  the  mouth  are  more  or  less 
painful.     They  both  develop  ^'ery  slowly  as  compared  with  syphilis. 


Fig.  216.^Ulcerating  gumma  of  soft  iKilatc  with  perforation. 

Cancer  is  always  indurated  (hard)  and  there  is  likely  to  be  a  cervical 
adenitis.  Tuberculosis  of  the  mouth  is  almost  always  secondary  to 
that  of  the  throat  or  lungs.  Finally,  there  is  the  Wassermann  test  for 
syphilis  and  the  therapeutic  test. 


^ 

"■"'      '^^■'' 

^■^ 

^Ib,  '^ 

K"'' 

-.  -'-. 

Fig.  217. — Syphilitic  leukoplakia.      (Dr.  Parounagian's  patient.) 


Leukoplakia. — This  consists  of  a  slight  thickening  of  the  mucosa 
which  assumes  a  pearly  white  or  pure  white  color.  It  may  occur  in 
from  pin-head-  to  split-pea-sized  areas  or  it  may  be  scattered  as  a  solid 
patch  over  the  mucosa  of  the  cheek  or  of  the  tongue  (Fig.  217).    Leuko- 


428  DERMATOLOGY 

plakia  is  not  always  syphilitic,  as  it  may  be  due  to  excessive  smoking 
or  to  irritation  from  fillings,  bridges,  etc.  In  any  event  leukoplakia 
must  be  considered  as  a  preepithelioma — a  forerunner  of  cancer. 

Syphilis  also  causes,  at  times,  an  atrophy  of  the  superficial  tissue 
of  the  tongue  with  the  result  that  the  lingual  surface  appears  smooth 
and  glistening.  On  the  other  hand  the  disease  may  produce  a  glossitis 
consisting  of  h^-pertrophy  instead  of  atrophy,  so  that  the  surface  of  the 
tongue  is  thickened,  thrown  into  folds  and,  perhaps,  fissured- — the 
so-called  scrotal  tongue. 


chaptp:r  XV. 

FACTORS  IX  PERSONAL  HYGIENE. 

By  C.  ward  CRAMPTON,  M.D. 

Racial  Hygiene. — The  subject  of  hygiene  is  one  of  the  most  impor- 
tant that  can  engage  the  attention  of  anyone.  •  Not  personal  hygiene 
alone,  but  racial  hygiene,  the  consideration  of  the  health,  illness,  birth 
and  death  of  whole  races  of  beings. 

Paleontology  teaches  us  that  various  forms  of  animals  once  lived 
on  this  earth  and  possessed  it;  huge  mastodons  and  dinosaurs,  and  other 
big,  strong,  wonderful  animals;  but  they  have  died,  and  their  species 
is  extinct.  Those  races  have  vanished.  Something  unhygienic  hap- 
pened. The  deduction  from  this  is  that  there  is  a  possible  peril  to 
the  human  race. 

There  are  signs  of  bad  hygiene  and  signs  of  impending  danger, 
and  perhaps  of  partial  death  of  the  race. 

Race  Death. — When  the  environment  of  a  race  changed  to  such  an 
extent  that  it  was  unable  to  adapt  itself  to  the  new  conditions,  it 
died.  Other  races  survived  because  they  w^ere  able  to  make  some 
slight  adaptive  structural  change  by  process  of  evolution,  fitting  them- 
selves to  the  changes  in  environment  and  making  further  progress. 
They  were  perhaps  the  progenitors  of  some  of  the  forms  of  life  today. 

The  Present  Emergency. — Today  the  human  race  is  changing  its 
environment  very  rapidly.  Within  a  few  thousand  centuries,  which 
is  a  very  short  time,  speaking  biologicalh^,  many  changes  have  been 
made,  one  of  the  most  important  being  the  gradual  change  from  rural 
to  city  life.  Two  hundred  years  ago  perhaps  not  more  than  5  per  cent, 
of  the  population  lived  in  the  city.  Today  45  per  cent,  of  the  people 
of  the  United  States  live  in  cities.  The  problem  of  the  human  race  of 
the  future  is  the  problem  of  the  city.  Now  that  means  bricks  instead 
of  trees,  asphalt  instead  of  brooks  and  fences,  and  the  iron  tramway 
instead  of  country  roads  and  the  good  solid  earth;  in  short  the  things 
that  are  hard,  things  that  bruise  and  tear  and  destroy  the  biological 
soundness  and  vitality  of  humanity.  Therefore  city  life  means  the 
relative  abandonment  of  the  hope  of  biological  continuance.  Put  the 
whole  human  race  in  cities  and  it  would  die.  It  is  rare  to  find  in  New 
York  City  a  grandchild  of  a  New  York  City  man  and  woman.  Races 
die  in  cities;  the  biological  strain  is  wiped  out. 

The  conditions  that  make  for  the  racial  death  in  cities  are  of  the 
greatest  concern;  they  are  problems  of  hygiene  and  of  health.  They 
are  not  matters  of  business  nor  of  politics  nor  of  art;  they  are  matters 
of  life  and  death,  not  of  the  individual  only  but  of  the  whole  race.  ^ 


430  FACTORS  IN  PERSONAL  HYGIENE 

The  biological  death  of  city  peoples  has  led,  of  course,  to  the  coming 
in  of  people  from  outside,  the  country  people  and  the  people  from 
abroad,  to  take  their  places.  The  country  boy  and  the  country  girl 
in  the  city  naturally  come  to  the  top  to  replace  those  at  the  top  that 
are  biologically  unfit.  That  explains  why  there  has  been  no  cry  of 
racial  degeneration  in  the  United  States  as  there  has  been  in  England 
and  in  Germany.  Four  or  five  years  ago  England  became  alarmed 
because  it  could  not  get  soldiers  of  the  requisite  height  and  strength. 
The  government  was  anxious  for  the  integrity  of  England  and  for  the 
health  of  Englishmen.  There  had  not  been  sufficient  influx  of  hardy 
lower  peoples  to  keep  the  race  up,  because  much  of  the  biological  cream 
of  England  had  been  skimmed  and  sent  over  to  the  United  States. 
And  in  Germany  the  same  thing,  to  a  somewhat  lesser  degree,  had 
happened.  This  is  the  reason  why  the  United  States  is  not  yet  alarmed 
over  a  similar  condition  of  affairs — the  racial  degeneration  of  old 
American  stock. 

Children  in  Schools. — So  much  for  the  importance  of  general  hygiene. 
The  dental  hygienist  will  deal  with  children  in  schools,  and  the  child 
in  school  will  be  found  a  very  different  thing  from  a  mere  child.  He 
becomes  a  unit,  one  of  a  hundred  or  a  thousand.  He  is  under  the 
teacher,  the  teacher  is  under  the  principal,  the  principal  is  under  the 
superintendent,  who  must,  in  turn,  look  to  the  Board  of  Education, 
or  the  school  committee.  The  child  in  school  is  not  a  child,  but  a  child 
in  relation  to  all  of  these  different  things;  and  the  hygienist,  going  into 
the  school,  must  know  where  she  and  her  work  may  stand  in  rela- 
tion to  the  other  teachers,  the  principal,  the  superintendent,  and  the 
Board  of  Education.  She  is  not  an  independent  person,  not  even  a 
dental  hygienist,  but  a  dental  hygienist  in  relation  to  all  of  these  per- 
sons and  the  influences  for  which  they  stand.  Therefore  it  is  necessary 
for  her  to  know  the  administrative  pulse  and  the  methods  and  ways  of 
conducting  school  affairs.  These  are  different  in  each  school  locality; 
it  is  for  the  hygienist  to  find  them  out,  for  she  will  do  her  best  work  in 
ways  that  are  known  to  the  pupils,  the  teachers,  and  the  principals. 
Forces  operating  along  certain  lines  are  found  in  schools,  which  cannot 
be  pushed  aside  and  cut  across  without  unnecessary  difficulty  and  fric- 
tion, but  if  the  hygienist  will  move  along  with  them  in  ways  that  are 
known,  efficiency  will  be  trebled.  In  other  words,  the  best  work  will 
be  accomplished  by  adjusting  the  work — and  oneself — to  existing 
methods.  If  the  work  is  carried  on  in  harmony  with  the  school  organ- 
ization, it  will  have  a  telling  effect;  otherwise  the  hygienist  in  the  school 
will  l)c  as  a  cinder  in  the  eye,  something  foreign  to  it,  which  will  cause 
trouble. 

Teaching. — The  business  of  the  school,  theoretically,  is  to  teach; 
practically,  it  is  to  develop  children  along  many  lines  besides  the  regular 
courses  of  stud\'.  There  is  a  subtle  difference  between  teaching  and 
developing  children.  They  may  sound  like  the  same  thing  but  it  is 
the  recognition  of  just  that  subtle  difference  which  has  led  to  the 


SUBJECTIVE  AND  OBJECTIVE  HYGIENE  431 

teaching  of  hygiene  in  an  entirely  different  way  from  that  which  foi-- 
merly  obtained.  The  old  method,  introduced  by  a  group  of  devoted, 
enthusiastic  and  very  efficient  women  interested  in  temperance  as  to 
alcohol  and  tobacco,  was  text-book  instruction.  Text-books,  every 
other  page  filled  with  warnings  of  the  dangers  of  alcohol  and  tobacco, 
were  put  into  the  hands  of  every  school  child.  On  the  statute  books 
of  most  of  the  States  is  a  requirement  to  the  efl'ect  that  certain  things 
shall  be  "taught  out  of  a  text-book,  and  the  text-book  shall  be  in  the 
hands  of  each  child."  It  may  readily  be  seen  that  a  much  greater 
emphasis  is  placed  upon  the  text-book,  than  upon  the  child.  Text- 
book instruction  has  resulted  in  the  forcing  of  information  upon  chil- 
dren, most  of  which  they  are  unable  to  grasp,  and  which  is  therefore 
a  failure. 

As  an  illustration  of  the  newer  methods  of  instruction,  the  things 
which  are  being  done  in  New  York  City  will  be  presented  briefly. 

SUBJECTIVE    AND    OBJECTIVE    HYGIENE. 

Objective  hygiene  is  the  doing  of  things  with  the  person  or  persons 
as  an  object,  such  as  surrounding  them  with  good  conditions  in  the 
schoolroom,  good  light,  heat,  ventilation,  etc.  In  this  group  also  fall 
physical  training,  athletics,  folk  dancing,  playing,  recesses,  and  other 
recreations.  The  hygiene  of  insirudion  comes  under  this  head.  The 
medical  inspection  of  the  pupil  is  at  first  objective,  and  then,  if  it  is 
to  be  successful  at  all,  it  leads  the  pupil  to  doing  things  for  himself 
and  becomes  subjective. 

The  teaching  of  health  laws  and  conditions,  on  the  other  hand,  is 
subjective.  It  is  the  endeavor  to  get  the  child  to  do  something  for 
himself,  to  inculcate  habits,  to  form  tendencies  for  right  action,  and 
leave  him  with  a  lasting  impression  that  will  affect  conduct. 

The  purpose  of  the  hygiene  of  instruction  is  the  counteracting  and 
elinjinating  of  health-depressing  influences  of  school  life.  It  is  not  only 
engaged  in  the  endeavor  to  keep  away  bad  things,  but  it  is  engaged 
also  in  the  endeavor  to  bring  good  things  into  the  school. 

The  earliest  efforts  were  made  toward  the  cure  of  disease  when  it 
already  existed;  next  came  the  prevention  of  disease;  and  now  the 
efforts  are  made  toward  acquiring  a  condition  of  euphoria  (which 
means  a  great  degree  of  vigor),  or  the  ability  to  cast  aside  all  disease 
influences. 

Each  of  these  courses  has  been  traveled  in  our  school  work,  and 
traces  of  the  earlier  stages  are  left,  as  the  cure  of  disease  and  its  pre- 
vention; but  the  most  modern  effort  is  toward  a  development  of  the 
superabundance  of  vigor,  health  and  happiness  of  the  children,  far 
beyond  the  mere  prevention  of  disease. 

The  hygiene  of  instruction  is  not  only  designed  to  counteract  and 
prevent  health-depressing  influences  of  school  life,  but  to  make  for 
stronger,  more  \igorous  lives  among  the  children.    This  method  con- 


432  FACTORS  IN  PERSONAL  HYGIENE 

trols  first,  the  seating  of  the  child.  The  school  desk  is  an  evil  of  long 
standing  in  the  schools.  Even  the  dental  hygienist  should  inform  her- 
self about  it,  for  it  will  avail  little  to  keep  a  child's  mouth  in  order  if 
he  is  allowed  to  sit  at  a  desk  which  necessarily  cramps  him  until  he 
is  crouched  over,  with  his  chest  caved  in  and  his  head  down  and  body 
twisted.  The  height  of  the  desk  should  be  such  as  to  permit  the  child 
to  sit  straight,  to  lean  forward  without  bending  except  at  the  hips, 
and  to  keep  the  body  straight;  to  be  able  to  place  the  hands  upon  the 
desk  so  that  the  fingers  may  be  held  properly  for  writing,  and  yet  that 
the  body  may  be  seated  against  the  back  of  the  chair. 

The  system  should  require  the  teacher  to  make  a  note  of  all  defects 
of  hearing  and  eyesight.  They  are  now  recorded  by  the  examining 
physician,  and  the  teacher  places  the  children  found  deficient  in  one 
of  the  front  rows. 

The  teacher  herself  may  be  called  upon  to  conduct  examinations 
in  sight  and  hearing,  and  in  default  of  an  efficient  medical  inspection 
system  the  hygienist  should,  if  possible,  induce  the  teacher  to  make 
the  tests  of  eyesight  and  hearing  herself.  The  following  case  is  of 
interest.  In  the  truant  school  there  was  a  boy  who  had  been  adjudged 
a  bad  boy  and  a  truant.  Something  about  his  eyes  attracted  attention, 
and  he  was  asked  to  read  from  a  book  which  was  handed  to  him.  It 
was  soon  found  that  he  could  not  do  it.  Books  with  larger  and  still 
larger  tj^e  were  given  him  and  finally  a  placard  with  letters  an  inch 
and  a  quarter  square,  and  it  was  only  by  bringing  this  huge  t^q^e 
within  six  inches  of  his  eyes  that  he  was  able  to  read  it.  That  boy 
was  not  so  much  a  truant,  or  a  bad  boy  as  a  blind  boy,  and  no  one 
knew  it.  If  such  a  case  can  be  pictured  to  the  imagination,  and  the 
damage  done,  not  alone  to  a  human  life  but  a  human  soul,  by  such 
stupid  and  almost  criminal  neglect  could  be  estimated,  the  advis- 
ability of  having  some  kind  of  hearing  and  vision  test  will  be  readily 
appreciated. 

The  temperature  of  the  schoolroom  should  be  kept  between  60°  and 
68°  F.  If  it  is  allowed  to  rise  above  70°,  it  is  bad  for  the  pupils  and 
teachers  and  for  the  efficiency  of  instruction,  and  the  temper  and 
spirits  of  both  pupils  and  teachers.  This  may  be  demonstrated  by  a 
person  trying  to  study,  first  in  a  room  which  has  a  temperature  of 
78°,  and  then  in  another  room  with  temperature  of  65°.  The  differ- 
ence will  be  obvious. 

Immobility. — There  is  another  important  point  and  that  is  immo- 
bility— that  is,  requiring  the  child  to  sit  still.  The  importance  of  tooth 
massage  by  tooth  use,  the  importance  to  the  tooth  of  its  daily  work  has 
recently  been  demonstrated  to  the  writer  by  Dr.  Fones.  The  rhythmic, 
alternate  compression  and  relaxation  occasioned  by  chewing  or  eating 
alternately  squeezes  the  bloodvessels,  and  then  allows  them  to  expand. 
All  tissues  of  the  human  body  depend  for  their  health  upon  massage 
of  this  kind.  The  reason  that  any  ill  health  of  the  digestive  tract 
exists,  for  instance,  is  because  peopje  have  become  sedentary  animals 


SUBJECTIVE  AM)  OBJECTIVE  HYGIENE  43.0 

instead  of  walking,  running,  jumping,  throwing,  swimming  animals, 
and  from  being  inactive  the  tissues  become  stagnant.  The  result 
of  tooth  stagnation,  caused  by  simply  swallowing  foorls  instead  of 
properly  chewing  them,  is  known  and  the  same  relative  harm  occurs 
to  the  whole  body  when  the  tissues  are  inactive  and  have  become  stag- 
nant. If  a  child  is  put  in  school  for  five  hours  each  day  and  required 
to  sit  still  during  all  that  time,  every  tissue  of  his  body  is  seriously 
damaged.  This  is  not  theory,  it  is  a  fact.  A  house  damaged  by  fire 
plainly  shows  the  damage,  but  that  done  to  the  body  can  only  be 
detected  by  such  signs  of  damage  as  the  hangdog  expression,  poor 
posture,  or  pallor. 

To  correct  this  the  following  directions  are  given  to  the  teachers 
for  use  in  the  lower  grades.  "  Care  should  be  taken  not  to  require  the 
children  to  sit  still  for  a  long  time.  In  addition  to  the  two-minute 
exercises  which  occur  three  times  a  day,  quiet  or  vigorous  games  may 
be  used  when  desirable,  and  every  hour  a  three-minute  recess  may  be 
given  in  which  free  movement  about  the  room  and  quiet  conversation 
are  allowed." 

This  is  but  a  poor  substitute  for  human  child  activity,  but  it  is  some- 
thing that  can  be  done,  while  if  the  children  were  turned  loose  to  act 
like  children  there  could  be  no  teaching  done. 

"In  the  first  and  second  years  the  children  may,  when  necessary, 
place  head  upon  the  arms  on  the  desk,  close  the  eyes,  and  relax  com- 
pletely for  a  moment  or  two."  This  is  one  of  the  most  human  things 
ever  seen  in  a  classroom.  Upon  a  signal  from  the  teacher  the  children 
simply  lay  their  heads  down  on  the  desk  and  act  as  if  they  were  asleep, 
and  it  is  quiet.  An  idea  of  what  that  means  to  the  nervous,  irritable 
child  of  the  city  streets  can  hardly  be  imagined.  It  is  like  a  breath  of 
fresh  air. 

Now  follows  the  school-teacher's  part  of  it. 

"The  children  should  be  called  to  strict  attention  immediately 
following  the  rest  periods.  Before  any  lesson  requiring  severe  concen- 
trated effort,  a  short  preliminary  relaxation  of  this  kind  is  most  help- 
ful and  the  contrast  between  the  rest  and  work  should  be  decidedly 
marked;  a  principle  of  very  great  importance." 

Further  directions  are  as  follows:  "Children  should  be  urged  to 
take  part  in  the  order  and  cleanliness  of  the  desks,  their  own  and  those 
of  the  classroom  at  large.  In  the  upper  grades  this  interest  should  be 
extended  to  the  school  and  community." 

"  The  light  should  fall  upon  the  desk  from  the  left  side.  Eyes  should 
never  be  closer  than  ten  inches  to  the  work."  Observation  in  the  school- 
room w^ll  probably  show  quite  a  number  of  noses  within  four  or  five 
inches  of  the  pen-point. 

"The  eyes  should  be  occasionally  raised  from  the  work.  Books 
should  be  held  off  of  the  desks  and  in  the  hands,  not  laid  down  upon 
the  desks."  If  the  book  is  laid  down  the  eye  is  placed  at  a  disadvan- 
tage, shortening  the  vision,  and  the  head  goes  down  and  then  the  hand 
28 


434  FACTORS  IN  PERSONAL  HYGIENE 

comes  up,  the  body  is  twisted  and  the  whole  child  slumps  down  in  a 
very  characteristic  and  common  fashion. 

Physical  Training. — Just  here  something  should  be  said  about  physical 
training.  This  includes  games  in  classroom,  playground  and  gym- 
nasium, and  gymnastics  of  a  formal  type  (i.  e.,  exercise  at  the  command 
of  the  teacher) ;  athletics,  folk  dancing,  and  the  like.  All  of  these  serve 
different  purposes  and  have  correspondingly  different  results,  which 
are  important. 

Educational  Exercises. — The  results  desired  from  physical  training 
are  various;  first,  neuromuscular  education,  which  is  a  mental  thing. 
The  muscles  have  nothing  to  do  with  it  except  to  abide  by  the  decision 
of  the  nervous  system,  which  is  trained  by  exercise.  Who  has  not 
seen  a  city  man  in  the  country,  particularly  going  down  to  a  float  on 
the  river  and  confronted  with  the  necessity  of  stepping  into  a  boat. 
He  will  approach  the  edge  of  the  float  with  great  care,  get  down  and 
grasp  something,  put  one  foot  in  and  then  perhaps  he  will  fall  over- 
board. He  is  a  motor  dullard,  and  the  motor  dullard  is  an  increasing 
character  of  our  population.  On  the  other  hand,  another,  no  doubt, 
would  walk  confidently  across  the  float,  step  in  the  boat,  grasp  the 
oars  and  row  away.  That  is  motor  ability  and  the  motor  dullard  can 
only  hope  to  acquire  it  by  exercise  and  training  of  the  nervous  system 
which  controls  the  motor  system.  All  of  the  seven  hundred  thousand 
youngsters  in  New  York  City  and  all  school  children  elsewhere  should 
have  that  kind  of  ability.  It  consists  in  coordination  of  the  various 
body  parts,  ability  to  move  with  precision,  ability  to  move  at  the 
right  time,  to  be  alert,  accurate,  definite,  complete  and  graceful  in 
movement.  ]\Iost  of  these  coordinations  are  unconscious,  the  result 
of  practise,  not  thought  about,  but  just  done.  Motor  education  is 
thus  one  of  the  greatest  things  in  physical  training. 

Hygienic  Exercises. — The  other  great  thing  resulting  from  physical 
training  is  health  of  body  tissue  by  means  of  exercise  of  the  muscles. 
When  the  muscles  are  exercised  everything  else  in  the  body  is  exercised, 
the  heart,  the  lungs,  the  arteries,  the  veins  and  the  nerves,  in  fact  the 
whole  body  is  made  to  work  in  exactly  the  way  it  was  intended  that  it 
should  work.  If  each  muscle  were  taken  separately  and  exercised  and 
brought  to  a  condition  of  health,  and  also  each  organ,  as  the  stomach, 
liver  and  spleen,  and  so  on  throughout  all  the  organs  of  the  body,  it 
would  prove  quite  a  task.  That  is  the  modern  method  of  education, 
by  the  way,  but  not  modern  physical  education.  Natural  exercises 
of  the  muscles  are  used  and  nature  stimulates  the  rest  of  the  body  in 
the  process  of  repairing  the  busy  muscles. 

The  method  of  evolution  has  been  such  that  those  whose  muscles 
have  been  exercised  in  walking,  jumping,  climbing  and  throwing  have 
survived,  and  those  anemic  beings  that  do  not  exercise  do  not  survive. 
So  our  ancestors,  in  their  more  active  physical  life  exercised  and  kept 
in  health.  Exercise  is  the  only  way.  Therefore  physical  training  is 
put  in  the  schools  to  make  the  tissues  of  the  children  healthy  and  strong. 


SUBJECTIVE  AND  OBJECTIVE  HYGIENE  435 

That  is  the  hygienic  side  of  physical  training,  a  very  different  thing 
from  the  educational  exercises  previously  described. 

Posture. — Next,  exercises  are  used  to  straighten  the  boys  and  girls. 
The  debutante's  dance  of  civilization  has  resulted  in  the  toleration  of 
such  things  as  the  debutante  slouch,  a  very  curious  thing  indeed;  but 
if  the  children  themselves  are  observed  it  will  be  seen  that  many  of 
them  have  a  slouch  of  the  same  kind.  The  chest  is  down  and  all  of 
the  contents  of  the  thorax  are  pressed  down  upon  the  abdomen,  which 
bulges;  the  head  is  hung  down  and  the  whole  attitude  is  a  picture  of 
dejection.  That  is  the  result  of  acute  or  chronic  fatigue,  occasioned 
by  bad  health,  lack  of  exercise,  bad  teeth  and  such  hygienic  errors. 
In  short,  poor  posture  is  a  depression  due  to  lack  of  tone.  Good  pos- 
ture on  the  other  hand,  is  an  attitude  of  vigor,  characterized  by  a 
raised  position  of  the  various  parts.  If  one  stands  tall,  with  head  and 
chest  held  high,  the  whole  body  and  the  mind  also  are  placed  at  the 
greatest  advantage. 

The  children  are  being  taught  to  stand  up  straight,  because  it  is 
a  sign  of  vigor,  and  in  itself  leads  to  a  better  state  of  health,  both 
physical  and  mental,  a  fact  easily  proven  to  oneself.  If  one  is  mentally 
depressed;  one  is  also,  as  a  rule,  physically  depressed,  and  if  he  will 
stand  up  straight  and  lift  his  chest  and  forcibly  get  away  from  the 
physical  depression,  a  mental  uplift  will  be  experienced.  Actually 
more  physical  and  mental  vigor  will  be  developed  by  using  this  very 
simple  and  cheap  device. 

Instruction  in  Hygiene. — The  purpose  of  instruction  in  hygiene  is  to 
inculcate  habits  of  cleanliness,  care  of  the  body,  good  posture,  etc., 
which  will  maintain  and  promote  good  health  and  this  superhealth, 
vigor.  The  emphasis  of  instruction  should  be  placed  upon  the  practical 
affairs  of  daily  life.  The  modern  method  of  education  is  one  that  takes 
the  subjects  and  experiences  of  life  and  uses  them  as  texts,  considers 
them  in  relation  to  something  new%  and  returns  to  the  child  a  habit, 
a  thought,  a  tendency  to  react  in  the  proper  way  toward  daily  life. 

Formerly-  a  different  method  was  used.  It  was  the  practice  to  present 
for  inspection  a  bone  that  the  child  had  never  seen  and  probably  never 
would  see  again,  and  consider  that  bone  and  other  bones  and  finally 
the  entire  skeleton.  Then  the  muscles  and  the  nervous  system  were 
considered  in  turn.  The  structures  of  the  body  mastered,  physiology 
was  studied  in  the  same  systematic,  logical  manner.  Then  the  children 
were  told,  in  effect,  "inasmuch  as  you  are  thus  made  and  inasmuch 
as  you  see  how  all  of  these  things  which  comprise  your  body  work  for 
your  good  or  ill,  >ou  will  readily  see  that  you  must  do  thus  and  so  in 
order  to  keep  well." 

The  structure  of  the  teeth  was  taught,  and  how  the  teeth  worked, 
and  finally  the  care  of  the  teeth.  Now,  in  teaching  hygiene,  it  is  pro- 
posed to  start  with  the  tooth-brush  and  the  use  of  the  tooth-brush 
daily,  four  times  a  day  and  two  minutes  each  time  ami  endeavor  to 
get  a  practical  result  immediately — the  habit  of  using  that  tooth-brush. 


436  FACTORS  IN  PERSONAL  HYGIENE 

It  matters  little  whether  the  six-year-old  child  knows  anything  at  all 
about  the  structure  of  the  teeth  or  not,  but  it  does  matter  much  whether 
or  not  he  learns  to  take  care  of  them.  Later  he  may  be  interested  in 
the  logical  way  in  understanding  what  he  has  been  doing,  but  children 
in  the  first  grade  in  the  elementary  school  are  not  logical  persons 
despite  the  fact  that  many  college  professors  are  attempting  to  raise 
their  children  upon  the  basis  of  the  theory  that  they  are. 

Hygiene  is  to  be  taught  upon  the  basis  of  telling  the  children  to  do 
things,  without  emphasis  upon  the  reasons  for  doing  them,  then  seeing 
that  they  do  them,  which  is  most  important  of  all,  and  last  comes  the 
logical  motivation.  The  strongest  and  most  effective  motivation  is 
compulsion.  This  may  be  reactionary,  but  it  is  effective.  There  are 
two  methods.  The  first  is  a  hygienic  inspection  of  each  child  every  day 
by  the  teacher,  the  object  of  which  is  to  get  the  child  into  the  habit 
of  coming  to  school  clean  and  orderly  in  person  and  in  clothing. 
Second,  to  render  concrete  and  practical  the  instruction  in  hygiene, 
to  determine  the  ability  of  the  pupil  to  put  into  practice  the  instruc- 
tion received.  They  are  told  to  do  something.  The  next  morning 
it  is  noted  whether  or  not  they  have  done  it.  Every  morning  the 
teacher  will  receive  the  pupils  at  the  desk  and  look  over  two  or  three 
points  among  the  following  which  are  considered  of  importance: 
cleanliness  of  face,  neck,  eyes,  nose,  teeth,  finger-nails  and  hair; 
collars,  waists,  caps,  shirts,  coats,  shoes,  outer  clothing,  handkerchiefs; 
books,  lunch  boxes,  and  desks.  This  daily  inspection  should  include 
as  many  details  as  practicable.  When  unhygienic  conditions  are 
discovered  an  endeavor  to  cure  them  should  be  made  by  conference 
with  the  individual  pupil  in  such  a  manner  as  not  to  occasion  embar- 
rassment. The  children  exliibiting  certain  symptoms  indicative  of 
disease  are  immediately  sent  to  the  physician.  When  this  daily 
inspection  of  the  children  can  be  held,  it  will  no  longer  be  a  common 
thing  as  it  once  was,  for  a  pupil  to  come  to  school  with  red,  inflamed 
eyes,  with  parasites  in  the  head,  with  dirty  clothes,  grimy  hands, 
black  finger-nails — meanwhile  getting  a  mark  pf  "perfect"  in 
hygiene  for  handing  to  the  teacher  a  very  carefully  prispared  picture 
of  the  skeleton  of  a  human  being. 

There  is  a  motivation  for  this  sort  of  interest  in  personal  hygiene 
and  that  is  the  desire  of  the  child  for  a])})r()])ation,  or  a  reward  of  some 
kind.  It  may  be  developed  iudi\'i<lually  or  upon  a  class  basis.  In 
certain  schools  in  New  York  placards  have  been  used,  which  have  a 
separate  column  for  the  records  of  each  day  of  the  week  or  month  as 
the  case  may  be.  One  placard  is  for  clean  teeth,  another  for  clean 
faces,  hands,  etc.,  and  so  on  through  a  selected  list.  The  teacher  tells 
the  children  that  on  the  next  day  she  will  conduct  an  insj)ection  of 
hands,  and  will  put  the  percentage  record  of  the  class  on  this  placard 
so  that  everyone  who  comes  in  may  see  what  the  standing  of  the  class 
is  in  the  matter  of  clean  hands.  Perhaps  twenty  will  be  found  to  have 
clean  hands  on  the  first  day  and  thirty  on  the  second.    Perhaps  the 


MY  DAILY   ROUTINE  437 

third  (lay  will  be  such  a  good  day  for  base-ball  that  there  is  but  slight 
gain — only  thirty-two;  the  teacher  then  imi)resses  the  point  that 
clean  hands  are  important,  and  succeeds  in  sending  the  record  up  to 
forty  on  the  fourth  day,  which  will  leave  but  a  few  of  those  who  are 
difficult  to  reach,  who  may  not  have  running  water  in  the  house,  or 
who  may  not  l)elieve  in  clean  hands  anyway,  but  with  some  effort 
fifty  may  be  reached.  The  next  day  it  may  be  that  one  is  absent  on 
account  of,  say,  toothache — due  of  course  to  lack  of  care  of  the  teeth. 
And  the  ensuing  days  as  they  come  along  each  provides  a  record  for 
that  class,  a  record  of  attainment,  a  record  in  which  all  are  interested, 
to  which  all  have  contributed,  and  of  which  all  are  immeasiu-ably 
proud.  It  is  an  effective  method.  The  more  it  is  considered,  the  more 
it  will  be  seen  that  it  appeals  to  many  different  kinds  of  human  motives. 
This  method  might  be  recommended  for  application  to  brushing  the 
teeth. 

The  second  important  new  method  is  the  endeavor  to  establish  a 
daily  routine  for  the  purpose  of  regulating  the  daily  health  schedule. 
The  teacher  is  requested  to  adapt  a  form  for  use  in  her  own  class, 
changing  it  from  time  to  time.  It  is  recommended  that  each  child 
shall  copy  the  schedule  for  himself  or  herself  and  take  it  home  for  his 
or  her  use.  It  should  be  hung  up  in  some  convenient  and  conspicuous 
place.  The  advantage  of  taking  this  schedule  home  is,  first,  that  the 
child  possesses  something  he  has  made  himself  and  which  hence  is 
very  much  better  and  more  effective  than  anything  the  Board  of 
Education  could  issue;  second,  that  the  parents  and  other  members 
of  the  family  see  the  schedule  and  read  it  at  least  once.  Possibly  one 
out  of  three  parents  will  become  interested  and  say,  "Well,  there  now% 
you  follow  that  or  I  will  whip  you,"  taking  the  cue  and  applying  it 
rapidly. 

The  following  is  a  daily  schedule: 

MY  DAILY  ROUTINE. 

Rise  as  soon  as  awake. 

Throw  bedclothes  over  foot  of  the  bed. 

It  was  found  necessary  to  change  the  "rising  as  soon  as  awake" 
to  "have  a  certain  time  for  rising  and  keep  to  it,"  or  words  to  that 
effect,  for  the  reason  that  the  child  ordinarily  took  this  too  seriously, 
pushing  aside  all  family  regulations  and  authority  and  getting  up  at 
any  time  at  all,  whether  daylight  or  not,  and  insisting  upon  staying 
up.  This  was  only  corrected  by  a  note  from  the  mother  to  the  principal 
saying,  "  Please  straighten  this  out  because  I  am  powerless  against  the 
authority  of  the  school."  At  times  this  authority  is  stronger  than 
we  know. 

Throwing  the  bedclothes  over  the  foot  of  the  bed  helps  to  air  the 
bed,  and  also  makes  it  a  place  less  comfortable  than  it  was  before 
and  is  therefore  conducive  to  getting  up. 


438  FACTORS  IN  PERSONAL  HYGIENE 

The  next  item  is  setting-up  and  deep-breathing  exercises.  Undoubt- 
edly a  large  number  of  New  York  City  children  do  this.  It  is  an  excel- 
lent thing  for  them,  or  for  anyone  to  do,  and  may  be  highly  recom- 
mended for  daily  practise,  even  for  dental  hygienists.  Teachers  of 
hygiene  and  physical  training  should  be  impressed  that  the  old  pro- 
\erb  "Shoemakers'  children  go  without  shoes"  is  one  to  which  they 
should  give  earnest  consideration,  and  that  they  should  take  exercise 
themselves  while  teaching  it  to  others.  Everyone  who  has  severe 
professional  duties  should  make  a  careful  search  for  the  proper  exer- 
cise to  be  taken  before  breakfast  in  the  morning  and  rigidly  adhere 
to  it. 

The  schedule  continues: 

Wash  with  hot  water  and  soap,  and  use  scrub-brush  on  face,  neck, 
and  chest. 

Use  cold  douche  on  neck  and  chest. 

Clean  finger-nails. 

Brush  the  teeth. 

Inspect  clothes  as  to  cleanliness. 

Prepare  for  breakfast. 

Walk  for  a  few  minutes  in  fresh  air,  if  possible. 

Use  clean  napkins  and  utensils,  eating  slowly  and  chewing  food  well. 

Attend  to  toilet,  washing  afterward. 

Prepare  for  school.    See  that  books  are  clean  and  in  order. 

Obey  rules  about  entering  school.  Be  punctual.  (The  principal 
put  that  in.) 

Take  care  of  clothing  and  give  attention  to  order  of  desk  in  school. 
Prepare  for  inspection. 

Be  careful  of  sitting  and  standing  posture  in  school. 

Drink  water  at  recess. 

Return  home  to  lunch  promptly. 

Play  in  fresh  air  after  school. 

Attend  to  study  of  lessons  and  finish  work  quickly. 

At  night  take  care  of  outer  clothing  in  preparation  for  bed. 

Attend  to  toilet,  wash,  put  clothes  and  school  books  in  order  for 
tomorrow. 

Open  windows  top  and  bottom. 

In  short,  these  are  affairs  of  daily  life.  They  are  things  of  actual 
experience  which  shoukl  be  regulated,  improved,  changed  and  made 
better  for  the  welfare  of  the  pupils.  It  is  a  very  different  thing  from 
book  learning. 

Brief  reference  may  be  made  to  the  great  development  of  tithletics 
in  New  York  and  other  cities,  that  brings  to  the  child  all  of  the  normal, 
strong,  competitive  play  happiness  that  would  belong  to  it  were  it  a 
normal  chikl  living  under  natural  conditions.  An  eft'ort  is  being  made 
to  i)iit  back  into  the  lives  of  the  chidh-cii  })ig  racial  experiences  of  run- 
ning anri  jumping,  ciiinbing,  throwing  ;ind  all  competitive  games  as  base- 
l)ull  and  basket-ball.     If  these  things  were  n(^t  actually  and  definitely 


MY  DAILY  ROUTINE  439 

put  into  the  lives  of  the  children  in  New  York  City  there  would  he 
a  f^eiieratiou  growing  up  through  a  })layless  childhood  to  be  a  menace 
to  the  race. 

For  the  girls  especially  there  have  l)een  brought  over  from  the  old 
world  the  charming,  rliythmic  play  dances  and  folk  dances  that  have 
been  danced  before  cottage  doors  of  the  different  countries  of  Europe. 
These  have  been  handed  down  from  generation  to  generation  of  chil- 
dren as  priceless  possessions  of  the  race.  These  play-forms  have  per- 
sisted l)ecause  they  have  been  good  and  strong  and  healthful  for  the 
children.  They  have  been  taken  and  lifted  from  their  natural  setting 
and  brought  over  to  catch,  as  it  were,  the  children  that  had  left  them 
behind  in  the  places  from  which  they  had  been  transported. 

Xow  our  big  groups  of  children,  tens  of  thousands,  even  hundreds 
of  thousands  that  have  come  from  eastern  Russia  are  given  a  chance 
to  dance  the  Komarinskaia  that  their  parents  once  danced  in  Russia. 
Stories  could  be  told  of  the  exhibition  of  feeling  on  the  part  of  parents 
that  have  come  from  Odessa  or  thereabouts,  upon  witnessing  their  own 
children  dance  the  dances  they  themselves  had  danced  so  long  ago  and 
so  far  away.  The  children  themselves  are  less  concerned  with  the  origin 
of  the  dance.  They  will  dance  an  Irish  jig  as  hap'pily  as  a  real  Russian 
dance,  and  the  Irish  children  joyously  swing  into  the  lilt  of  the  Russian 
and  Italian  dances. 

Reference  may  also  be  made  to  the  playground  movement.  Dur- 
ing 1913-1914  one  hundred  and  ten  big  public  school  playgrounds 
have  been  opened  in  congested  portions  of  the  city,  and  in  these 
the  children  are  given  a  chance  to  play.  They  have  big  iron  gates, 
and  where  it  was  once  a  common  sight  to  see  the  dirty  street 
crowded  with  a  heterogenous  mass  of  children  outside  of  these  gates 
(now  that  the  playgrounds  are  finally  opened),  one  hundred  and  twenty 
thousand  of  them  are  playing  in  safety  the  games  that  belong  to  child- 
hood. So  these  are  the  things  which  make  up  the  essentials,  and  which 
are  typical  of  the  campaign  for  racial  health  under  the  conditions  im- 
posed by  the  city  and  the  growth  and  development  of  the  race  up  to 
its  present  civilized  state.  The  share  of  the  dental  hygienist  in  the 
work  of  racial  hygiene  is  of  far  greater  importance  than  it  has  been 
possible  to  indicate  here. 


CHAPTER  XVI. 

FRESH  AIR  AND  CORRECT  POSTURE  IN  THEIR 
RELATION  TO  HYGIENE. 

By  professor  IRVING  FISHER. 

A  COMPREHENSIVE  study  of  the  various  aids  to  health  is  a  necessary 
part  of  the  equipment  of  a  dental  hygienist  if  she  is  to  practise  her 
specialty  with  any  degree  of  intelligence.  Her  life-work  is  to  be  devoted 
to  the  prevention  of  oral  lesions.  The  assistance  of  healthy  bodies  in 
the  patients  that  come  under  her  care  will  do  much  toward  making 
her  work  a  success.  Hence,  if  she  has  so  trained  herself  as  to  be  able 
to  give  these  patients  proper  suggestions  in  the  form  of  hygienic  rules 
whereby  they  may  biung  their  bodies  up  to  the  normal  state  of  resis- 
tance and  health,  she  will  have  increased  her  sphere  of  usefulness  to  a 
marked  degree.  From  such  a  viewpoint  the  subject  matter  of  this 
chapter  becomes  at  once  of  much  practical  importance. 

There  has  been  formed  recently  in  this  country  an  organization 
known  as  the  Life  Extension  Institute,  the  object  of  which  is  to  pro- 
mote an  interest  in  personal  hygiene.  The  Hygiene  Reference  Board 
of  this  Institute,  of  which  the  writer  is  a  member,  has  formulated  cer- 
tain rules  of  hygiene  which  may  be  classified  under  four  headings: 
(a)  air  hygiene,  (h)  food  hygiene,  (c)  activity  hygiene,  and  (d)  rest 
hygiene. 

Under  air  hygiene  there  are  four  rules: 
L  Let  the  fresh  air  in. 

2.  Go  out  after  it. 

3.  Sleep  in  it,  if  possible. 

4.  Breathe  deeply. 

1 .  Let  the  Fresh  Air  In. — Mankind  now  lives  in  houses  which  shut 
out  the  fresh  air,  to  which  primitive  man  was  accustomed,  and  inter- 
fere with  its  circulation,  a  fact  which  undoubtedly  has  much  to  do  with 
the  value  of  the  fresh-air  cure.  It  is  not  simply  a  matter  of  the  fresh- 
ness of  the  air,  but  also  its  motion  and  coolness  which  are  largely 
responsible  for  its  healthfulness. 

Ordinarily,  house  air  is  bad  because  it  is  not  fresh,  not  in  motion, 
and  is  often  too  hot  and  too  moist.  A  gentle  draft  is  an  excellent  thing. 
Of  course  if  the  skin  is  not  adapted  to  it  through  exercise  and  is,  as  a 
result,  practically  half-(k'a(l,  the  blood  has  not  l)een  ])ro])erly  oxygenated, 
anfl  one  is  in  a  condition  to  be  infected  with  any  germ  that  may  happen 
to  be  present.  Tender  such  circumstances  a  draft  may  produce  a  cold, 
but  even  a  big  draft  will  not  have  such  an  efl'ect  if  one  has  accustomed 


LET   THE  FRESH  AIR  IN  441 

his  skin  to  an  oiitdooor  life.  Therefore  the  hermetically  sealed  room 
is  a  menace,  not  only  because  the  air  is  not  fresh,  but  because  there  is 
no  circulation  of  air.  It  is  a  great  help,  even,  to  have  an  electric  fan 
going  in  a  room,  especially  where  there  is  no  real  ventilation. 

Outside  air  should  be  let  in  so  that  there  will  be  more  freshness, 
motion,  coolness  and  dryness.  Fresh  damp  air,  however,  is  preferable 
to  close  dry  air,  the  fear  of  dampness  being  one  of  the  many  old-fash- 
ioned health  superstitions.  It  is  better  to  sleep  out  of  doors  in  foggy 
air,  than  to  sleep  indoors  in  ideally  dry  air.  In  fact,  air  may  be  too 
dry  as  wtII  as  too  moist,  and  generally  is  so  in  our  houses  in  winter, 
the  humidity  often  being  as  low  as  8  to  10  per  cent,  of  saturation, 
whereas  it  should  be  about  40  per  cent,  for  health.  The  humidity  of 
fog  is  100  per  cent.,  and  yet,  if  all  other  characteristics  of  fresh  air  are 
present,  it  is  not  unhealthful. 

But  how  is  the  fresh  air  to  be  let  in?  The  best  way  is  to  open  the 
windows,  the  objection  to  this  being  that,  in  the  winter  time,  generally, 
the  air  flows  in  over  the  windows-sill  down  to  the  floor  and  makes  the 
feet  cold,  while  the  lungs  fail  to  get  the  benefit  of  it.  Unless  the  air 
is  introduced  intelligently  through  the  windows  they  might  almost 
as  well  remain  closed.  It  is  quite  a  simple  matter  to  introduce  out- 
side air  into  a  room  through  an  open  window  in  such  a  manner  that  it 
will  not  flow  down  on  the  floor  and  chill  the  feet  but  will  shoot  up  to 
the  ceiling  and  then  come  down  like  a  shower  all  over  the  room  to  fill 
the  breathing  zone  where  it  is  wanted.  This  may  be  done  by  means 
of  a  window  board,  a  board  about  three  or  four  inches  high  placed 
vertically  across  the  inner  side  of  the  window-sill,  that  is,  in  front  of 
the  bottom  of  the  window  but  as  far  away  from  the  window  as  the  sill 
will  allow,  which  is  usually  from  two  to  four  inches.  If  the  window  is 
opened  not  more  than  the  height  of  this  board  the  air  that  flows  in 
strikes  this  board  and  is  deflected  upward  instead  of  going  down  to 
the  floor  as  it  would  if  the  board  were  not  there.  The  air  will  continue 
on  its  way  upward  far  beyond  the  height  of  the  board,  for  it  clings  to 
the  window,  by  virtue  of  a  law  of  air  motion  whereby  it  follow^s  a 
surface.  Air  does  not  leave  a  surface  until  it  has  been  in  contact 
with  that  surface  for  a  comparatively  long  time,  so  that  it  may  be  car- 
ried even  up  to  the  ceiling  to  which  it  will  cling  in  turn,  traveling 
toward  the  center  of  the  room  before  it  drops  down.  In  this  way  air 
may  be  forced  to  distribute  itself  throughout  a  room  instead  of 
forming  a  cold  layer  on  the  floor  to  chill  the  feet,  while  the  rest  of 
the  room  is  filled  with  air  that  is  hot  and  bad  for  breathing. 

A  room  should  be  thoroughly  aired  before  being  occupied,  and  while 
occupied  there  should  be  a  continuous  current  flowing  through  it.  If 
it  is  possible  to  arrange  for  a  cross  draft  a  much  greater  circulation  is 
created  than  when  the  air  comes  in  only  at  one  window,  finding  its 
way  out  as  best  it  may,  through  keyholes  and  tiny  cracks  here  and 
there. 

Man  was  originally  an  outdoor  animal  and  it  has  been  impossible 


442         FRESH   AIR  AND  CORRECT  POSTURE 

for  him  to  break  away  from  his  inheritance  entirely.  It  is  but  half 
a  century  since  Darwin  propounded  the  theory  that  the  human  race, 
instead  of  being  an  independent  creation,  has  descended  from  the 
same  stock  as  did  the  anthropoid  apes.  That  conclusion  is  now  gener- 
ally accepted. 

These  primates  had  no  houses  but  lived  in  jungles;  their  descend- 
ants, our  ancestors,  lived  in  caves,  and  not  in  hermetically  sealed 
houses.  x\nd  even  after  w^ll-built  houses  came  into  use  with  following 
generations,  there  was  still  plenty  of  ventilation  until  glass  was  devised, 
when  it  was  discovered  that  light  could  be  let  in  without  letting  in 
the  air,  one  serious  consequence  of  which  has  been  that  the  human 
race  has  been  made  the  victim  of  tuberculosis.  That  is  the  price  that 
had  to  be  paid  for  running  counter  to  nature.  It  is  one  of  a  hundred 
examples  where  civilization  has  upset  the  equilibrium  of  nature. 
]\Iankind  today  does  not  live  biologically  or  physiologically,  because 
the  conditions  which  civilization  imposes  are  foreign  to  the  nature  of 
his  body.  He  was  adapted  for  life  in  the  open  just  as  the  monkey  was. 
Therefore  he  lives  at  his  peril  in  air-tight  caves  and  must,  if  he  would 
be  healthy,  recognize  the  necessity  of  restoring  the  original  conditions 
to  the  extent,  at  least,  of  letting  the  fresh  air  in. 

2  and  3.  Go  out  after  fresh  air  and  sleep  in  it,  do  not  depend 
entirely  upon  ventilation,  for  it  is  possible  to  get  ever  so  much  better 
results  by  being  real  outdoor  men  and  women.  Evidence  such  as  is 
portrayed  in  the  lives  of  centenarians  and  in  the  high  death-rate  among 
those  whose  occupations  keep  them  indoors,  and  the  low  death-rate 
among  those  who  have  outdoor  occupations  demonstrates  how  great 
a  benefit  is  the  living  out  of  doors.  There  is  something  about  the  out- 
door air  that  is  very  diflf'erent  from  that  indoors.  Living  in  a  well- 
ventilated  room  is  not  the  same  as  actually  being  out  in  the  air.  It 
is  sometimes  thought  that  this  is  due  to  certain  electrical  conditions, 
ozone  perhaps,  or  the  difference  in  the  motion  of  the  air,  or  variation  in 
the  radiation  of  light.  It  has  been  suggested  also  that  while  in  the 
open  the  body  radiates  heat  in  every  direction,  but  that  indoors  this 
heat  is  thrown  against  the  ceilings  and  walls  and  comes  back  to  the 
body.  These,  of  course,  are  but  theories,  not  actually  proven  as  yet. 
Professor  C.  E.  A.  Winslow,  Professor  of  Public  Health,  Yale  Univer- 
sity, Dr.  James,  of  New  York,  Fliigge  and  Paull,  of  Germany,  have  been 
working  on  this  problem  and  all  have  come  to  the  conclusion  that  it 
is  not  a  matter  of  the  chemical  content  of  the  air  as  was  formerly 
believed.  The  number  of  grains  of  carbon  dioxid  in  each  cubic  foot  of 
air  was  at  one  time  held  responsible  for  air  conditions.  Experiments 
have  since  shown,  however,  that  air  in  which  the  dioxid  content  has 
been  very  high  has  not  subjected  the  person  in  such  environment  to 
headache  or  to  a  sense  of  closeness.  As  an  instance,  an  experiment  was 
mafle  in  (icrinany  wherein  a  ])erson  was  i)lacc(l  in  a  box,  fresh  air 
being  supplied  to  him  through  a  tube  from  the  outside,  in  spite  of  which 
he  complained  of  headache  and  a  sense  of  closeness.     His  breathing 


HUE  AT  II R  DEEPLY  443 

was  all  right,  the  air  that  ])asse(l  into  the  knifes  was  pure,  yet  the  fact 
that  the  body  was  not  surrouiuleil  by  fresh  air  made  something  wrong. 
In  all  probability  it  was  that  the  heat  of  the  body  could  not  disappear 
as  rapidly  as  when  it  was  bathefl  in  normal  air. 

Following  this  came  another  experiment  in  which  conditions  were 
reversed,  the  person  being  placed  outside  of  the  box  in  the  fresh  air, 
with  a  tube  through  which  to  breathe  the  bad  air  from  the  box.  It 
was  found  that  no  symptoms  of  headache  appeared  as  long  as  the  body 
was  exposed  to  the  free-flowing  fresh  air  outside.  This  would  tend  to 
show  that  the  air  with  which  the  body  comes  in  contact  is  fully  as 
important  as  the  air  from  which  the  lungs  are  filled. 

In  the  same  country  another  experiment  was  made,  this  time  upon 
a  cat,  which  was  put  in  a  rubber  foot-ball,  with  the  result  that  the  cat 
soon  died.  Again  a  cat  was  placed  with  its  head  only  in  the  foot-ball 
and  this  cat  did  not  die;  it  lived  on  indefinitely  as  long  as  its  body  was 
exposed  to  good  air.  Therefore,  it  w^ould  seem,  that  to  obtain  any  bene- 
fit from  being  out  of  doors  one  must  not  simply  snift"  the  fresh  air 
through  a  crack  in  the  window  or  even  sleep  with  head  alone  out  of 
the  window,  as  was  tried  in  the  treatment  for  tuberculosis  a  few 
years  ago.    It  seems  necessary  to  be  out  altogether. 

Since  the  contact  of  the  air  with  the  skin  is  so  important,  air  is  evi- 
dently needed  not  only  for  filling  the  lungs,  but  for  covering  the  body. 
Why  this  is  so  is  not  exactl\'  known.  ]\Iaybe  because  heat  can  pass 
more  quickly  from  the  body,  or  that  waste  products  are  eliminated 
by  the  action  of  the.  air  on  the  skin.  At  any  rate  it  seems  perfectly 
evident  that  the  body  should  be  in  the  air.  Before  going  to  bed  at 
night  and  upon  rising  in  the  morning  are  convenient  times  for  real 
air  baths,  and  it  is  well  to  emphasize  the  fact  that  an  air  bath  is  quite 
as  important  as  a  water  bath.  It  is  also  possible  for  one  to  get  an  air 
bath  even  when  fully  clothed  if  the  clothes  are  of  such  texture  as  to 
allow  the  air  to  come  in  contact  with  the  skin.  For  this  reason  porous 
clothes  are  much  better  than  closely  woven  garments  and  linen,  and 
good  conducting  material  better  than  woolen  and  other  bad  conduct- 
ing material.  The  old  idea  of  swaddling  clothes,  woolen  underclothes 
and  tightly  woven  underclothes  meant  that  the  skin  was  virtually 
being  smothered.  The  clothes  should  be  ventilated,  as  well  as  the 
house,  and  they  should  be  porous  through  and  through.  When  wear- 
ing such  clothes  it  will  be  noted  that  the  air  will  be  felt  against  the 
skin,  while  persons  clad  in  ordinary  garments  do  not  recognize  that 
there  is  any  air  stirring.  The  wearing  of  porous  garments  will  make 
the  skin  healthy,  and  from  being  waxy  white,  it  will  show  a  glow  of 
health.  And  why  not  acquire  red  healthful  bodies,  as  well  as  red 
cheeks,  from  outdoor  air? 

4.  Breathe  Deeply.— The  following  illustration  from  life  serves  well 
to  impress  this  rule.  It  refers  to  a  certain  professor  of  philosophy 
who  broke  down  nervously  and  was  told  by  his  physicians  that  he 
would  never  be  able  to  do  literary  work  again.    He  tried  all  sorts  of 


444         FRESH  AIR  AND  CORRECT  POSTURE 

hygiene  as  they  were  presented  to  him  and,  although  ahvays  obtaining 
some  benefit  for  the  effort,  he  would  break  down  again  upon  returning 
to  work.  Finally,  having  tried  about  everything  else  he  decided  to 
study  the  Hindoo  methofl  of  deep  breathing.  It  is  said  that  the  Hin- 
doos use  this  faithfully  and,  being  a  philosopher  and  interested  in  meta- 
physics, religion  and  theology,  he  began  to  read  books  on  these  sub- 
jects, whose  authors  associate  certain  physical  exercises  with  their 
religion  and  philosophy,  and  have  always  claimed  that  the  breath 
is  closely  related  to  the  mind.  He  decided  that  he  would  go  to  the 
Ural  ^Mountains  in  the  south  of  Russia,  and  spend  three  months  in 
deep  breathing.  He  practised  slow,  deep  breathing  for  an  hour  at  a 
time,  sitting  erect  in  a  chair,  or  lying  straight  out  on  a  bed  and  breath- 
ing as  deeply,  slowly  and  evenly  as  possible.  The  result  was  that  he 
completely  regained  his  wonderful  vitality. 

Kant,  the  great  philosopher,  worked  out  some  ideas  on  deep  breath- 
ing before  the  physiological  explanation  was  known  at  all,  little  even 
being  known  of  anatomy  and  physiology.  He  practised  deep  breathing 
while  walking  about  the  streets.  His  belief  was  that  the  air  circulated 
through  his  brain,  enabling  him  to  think  better.  He  did  not  realize 
the  physiological  fact  that  the  body  required  it  to  go  through  his  lungs 
and  from  there  into  the  blood.  He  arrived  at  the  truth  without 
knowing  the  basis  of  it. 

A  very  good  way  to  make  sure  that  one  is  breathing  evenly  is  to 
stop  one  nostril  with  the  finger  and  breathe  through  the  other  nostril. 
When  this  is  done  it  is  possible  to  hear  the  air  drawn  in  and  any  uneven- 
ness  of  breathing  can  be  detected.  This  should  be  done  first  with  one 
nostril  and  then  the  other  until  a  habit  of  even  breathing  is  estab- 
lished. Instead  of  breathing  eighteen  times  a  minute  as  ordinarily, 
respiration  should  be  reduced  gradually,  to  three  or  even  two  times  a 
minute.     At  no  time,  however,  should  it  be  uncomfortably  low. 

It  has  been  demonstrated  that  rapid,  deep  breathing  Avithout  mus- 
cular exercise  may  result  in  illness.  Professor  Henderson,  of  Yale 
University,  has  made  a  comprehensive  study  of  blood-pressure  and  the 
oxygenation  of  the  blood,  and  has  found  by  experiment  that  if 
deep  breathing  be  forced,  it  so  upsets  the  vital  equilibrium  as  to  actually 
do  injury  instead  of  being  of  benefit.  Nature  prescribes  that  there 
shall  be  an  appetite  for  fresh  air  before  it  is  taken  in,  just  as  that 
there  shall  be  an  appetite  for  food  before  it  is  eaten  and  to  gorge  one- 
.self  with  fresh  air  is  harmful,  as  it  is  to  gorge  oneself  with  food.  For 
this  reason  exercise  in  connection  with  fresh  air  is  very  beneficial, 
because  it  creates  a  hunger  for  air.  Ordinarily  exercise  and  fresh  air 
should  go  hand-in-hand,  but  this  slow,  deep  breathing  is  practised  to 
better  advantage  without  exercise.  The  benefits  of  slow,  deep  breath- 
ing are  many.  First,  the  air  gets  into  the  more  remote  parts  of  the 
lungs.  Ordinarily  the  tidal  air  or  the  air  going  in  and  out  of  the  lungs 
at  each  respiration  is  but  10  per  (;ent.  of  the  air  content  of  the  lungs; 
that  is,  for  every  100  cubic  centimeters  of  air  only  10  cubic  centimeters 


BREATHE  DEEPLY  445 

go  in  and  out  tluring  ordinary  breathing.  In  deep  breathing  the  hnigs 
are  almost  wholly  emptied  and  refilled  from  top  to  bottom,  and  so 
contain  purer  air,  while  more  parts  of  the  limgs  are  used.  As  a  result 
the  ai)ices  of  the  lungs,  where  tuberculosis  usually  starts,  resist  disease, 
and  do  not  become  anemic  but  rather  are  exercised,  oxygenized  and 
have  vital  force  brought  to  bear  upon  them  so  that  they  are  kept 
healthy. 

In  the  second  place,  deep  breathing  calms  the  mind;  just  why  it  is 
hard  to  say  exactly,  but  it  is  so.  The  Hindoos  found  this  out  before  the 
scientists  studied  it,  and  there  seems  to  be  no  doubt  that  they  have 
the  right  idea  about  it.  There  is  certainly  a  strong  relation  between 
the  mind  and  the  breath.  When  one  feels  sad,  the  first  inclination  is 
to  sigh,  sighing  being  but  a  modified  breathing.  When  one  is  fright- 
ened, the  breath  will  usually  stop  for  the  fraction  of  a  moment,  after 
w^hich  comes  a  sudden  expiration.  When  angry,  the  breath  comes 
fast.  The  breathing  will  respond  to  the  mental  condition  very  quickly. 
Of  course  the  mental  condition  will  also  affect  the  heart  beat,  as  well  as 
many  other  functions  of  the  body,  but  there  seems  to  be  a  very  definite 
relation  between  the  mind  and  the  breathing.  It  is  often  found  that 
a  person  who  is  nervous,  overstrung  or  working  too  hard,  or  one  sufi'er- 
ing  with  neurasthenia,  who  is  shy  and  timid,  afraid  to  approach  people 
or  has  that  peculiar  fear  that  goes  with  certain  kinds  of  neurasthenia, 
will  often  breathe  in  an  irregular  manner.  If  there  is  mental  trepida- 
tion, there  is  trepidation  in  the  breath;  if  there  is  mental  calm,  there 
is  calmness  in  the  breath. 

The  muscles  of  breathing  are  peculiar  muscles;  they  are  "semivol- 
untary."  They  operate  ordinarily  without  thought,  and  during  sleep 
they  work  up  and  down  just  as  the  heart  beats  back  and  forth.  Much 
of  the  time  one  is  not  conscious  of  their  working  there  is  no  volition. 
However,  if  one  wishes  to  he  can  take  a  long  breath,  fast  or  slow,  as 
he  likes,  so  these  muscles  are  called  semivoluntary.  If  left  alone  they 
work  themselves,  that  is,  the  lower  nerve  centers  work  them,  but  they 
are  also  controllable  by  higher  nerve  centers  connected  w^th  the  mind. 
It  is  probably  because  of  this  double  control,  voluntary  and  in^'olun- 
tary,  that  the  character  of  the  breathing  exerts  such  an  influence  on 
the  mind.  At  any  rate,  if  one  breathes  slowly  and  rhythmically,  it 
will  tend  to  calm  an  agitated  mind,  and  will  often  work  as  a  cure  for 
nervous  prostration  if  persisted  in  systematically  for  a  long  time. 

In  the  third  place,  deep  breathing  is  advantageous  because  it  emp- 
ties the  portal  circulation,  and  this  introduces  the  second  part  of  the 
subject  of  the  text,  i.  e.,  posture,  which  at  first  thought  may  seem  to 
have  very  little  to  do  with  fresh  air. 

Deep  breathing  empties  the  portal  circulation  of  stagnant  blood, 
and  at  the  same  time  it  supplies  oxygen  to  purify  that  blood  as  it  goes 
through  the  lungs,  and  takes  the  carbon  dioxid  away.  It  enables  the 
nutritive  processes  to  go  on  in  the  liver  and  the  intestines  without 
their  being  poisoned  by  this  stagnant  pool  of  blood  which  so  many 


446         FRESH  AIR  AND  CORRECT  POSTURE 

people  carry  about  with  them  all  the  time.  Deep  breathing  pumps 
that  stagnant  pool  dry,  as  it  were,  and  also  pumps  out  the  stagnant 
blood  in  the  liver,  which  is  closely  connected  with  the  portal  circulation, 
a  system  of  bloodvessels  connecting  the  liver  with  the  intestinal  tube. 
These  vessels  are  so  large,  so  capacious,  that  they  are  capable  of 
holding  all  the  blood  of  the  body,  but  if  this  system  of  bloodvessels 
should  collapse  and  absorb  the  blood  of  the  body,  a  person  would 
bleed  to  death  without  any  blood  coming  out  of  the  skin,  the  blood 
merely  sagging  down  into  the  abdomen.  That  sometimes  happens, 
often  after  a  surgical  operation  and  is  what  is  called  "shock,"  but 
if  the  simple  physical  mechanism  that  produces  shock  were  better 
known  and  the  methods  of  preventing  it,  many  of  these  cases  of  death 
from  shock  could  be  avoided.  Sometimes  a  person  will  faint  because 
the  nervous  equilibrium  is  upset;  this  causes  the  bloodvessels  to 
expand,  the  blood  goes  into  the  portal  circulation,  the  supply  of  blood 
to  the  head  is  almost  depleted,  not  leaving  enough  to  keep  the  brain 
working  and  consciousness  is  lost. 

A  surgeon  should  take  the  blood-pressure  of  his  patient  before  and 
after  operation.  The  importance  of  so  doing  may  be  well  illustrated 
by  the  following  case.  A  certain  surgeon  took  the  blood-pressure  of 
his  patient  after  an  operation,  finding  that  the  instrument  registered 
practically  zero — the  blood-pressure  of  a  dead  person.  Instead  of 
deciding,  as  manj^  might  have  done  that  the  patient  was  dead,  or  at 
least  past  all  help,  this  man  realized  that  the  trouble  was  that  all  the 
blood  had  gone  into  the  portal  circulation  through  the  nervous  shock 
of  the  operation  and,  by  tying  a  bandage  around  the  abdomen  of  the 
patient  and  putting  a  hot-water  bag  under  the  bandage  wuth  a  tube 
attached,  into  which  he  blew  air,  caused  pressiu-etobe  distributed  evenly 
over  the  abdomen  which  squeezed  the  blood  out  of  the  portal  circula- 
tion and  congested  liver.  This  drove  the  blood  into  the  bloodvessels 
of  the  body  where  it  belonged,  raised  the  blood-pressure  and  in  a  short 
time  consciousness  returned.  That  man  owed  his  life  to  the  fact  that 
the  surgeon  understood  the  mechanism  of  the  portal  circulation. 

Few  ])eople  realize  how  large  {)  part  the  portal  circulation  plays  in 
their  daily  life  or  how  often  they  upset  its  equilibrium.  It  is  provided 
with  a  system  of  nerves  and  muscles,  just  as  is  every  other  bloodvessel. 
These  nerves  and  muscles  are  known  as  dilators  and  contractors  of 
the  vessels  and  under  normal  conditions  are  adjusted  to  meet  the 
requirements  of  the  body.  So  far  as  the  contractors  are  concerned, 
nature  depends  upon  a  certain  amount  of  help  or  reinforcement  from 
the  pressure  of  the  muscles  of  the  abdomen.  She  expects  a  person  to 
keep  erect,  which  is  the  natural  j)ostiir(',  so  that  there  will  be  a  certain 
pressure  within  the  abdoiiieii  from  the  muscles  that  are  })ulled  taut 
by  the  position  of  the  body.  In  other  words,  every  person  who  sits 
and  stands  erect  exerts  a  certain  amount  of  pressure  upon  the  portal 
vessels  by  the  tension  of  the  abdominal  muscles.  Upon  assuming  a 
slouching  position  this  ])ressure  is  immediately  relaxed  and  nature 


IMPORTANCE  OF   CORRECT   POSTURE  447 

cannot  accomplish  her  full  work.  While  a  perfectly  well  person  might 
afford  to  "slouch"  for  years  without  apparent  injury,  yet  it  is  plain 
that  the  strain  upon  the  contractors  forces  them  to  do  more  work  to 
compensate  for  the  lessened  work  of  the  abdominal  muscles.  The 
strain  is  analogous  to  eye-strain  and  has  similar  effects.  If  the  ])erson, 
however,  becomes  undertoned,  and  overstrains  his  general  nervous 
system,  there  is  not  enough  nervous  force  generated  to  keep  the  portal 
vein  closed,  and  it  will  finally  collapse.  The  contractors  cease  function- 
ing owing  to  fatigue,  and  a  form  of  nervous  prostration  called  splanch- 
nic neurasthenia  is  produced,  one  of  the  chief  symptoms  of  which  is 
"the  blues,"  and  which  can  usually  be  traced  to  an  excess  of  blood  in 
the  portal  circulation,  very  probably  due  to  habits  of  slouching  in 
sitting  and  standing,  for  such  habits  may  very  reasonably  be  con- 
sidered as  predisposing  causes  of  disease.  This  is  because  the  stag- 
nant portal  blood  stream  becomes  filled  with  poison  and  the  blood 
therein  is  in  no  condition  to  properly  nourish  the  body,  so  that  the 
individual  becomes  an  easy  prey  to  tuberculosis  or  any  infectious 
disease. 

Miss  Jessie  H.  Bancroft  of  the  American  Posture  League  has  com- 
piled a  book  emphasizing  correct  posture  for  school  children  and 
tlirough  its  pages  has  made  an  effort  to  improve  the  conditions  in 
schools,  advocating  special  chairs  and  various  other  changes  in  equip- 
ment to  overcome  bad  posture.  Chairs  are  responsible  for  a  great 
deal  of  nervous  prostration  because  they  are  apt  to  be  built  to  induce 
slouching  positions,  and  are  but  another  illustration  showing  how 
civilization  has  upset  the  equilibrium  of  nature.  Chairs  are  made 
wrong,  and  the  effect  has  been  overlooked.  This  defect  of  the  ordi- 
nary chair  may  be  overcome  by  placing  a  cushion  at  the  small  of 
the  back  so  that  the  abdominal  muscles  are  made  taut,  and  it  will 
be  found  that  long-continued  work  will  not  be  so  tiring  if  the  back 
is  properly  supported. 

One  way  to  force  the  blood  out  of  the  abdomen  is  to  lie  face  down- 
ward with  a  pillow  under  the  abdomen,  bringing  the  pressure  thereon. 
Dr.  Osier  recommended  a  patient  to  lie  on  the  back  and  roll  a  small 
cannon  ball  over  the  abdomen.  Another  way  is  to  take  deep  breaths 
in  the  right  posture,  breathing  with  the  diaphragm  as  much  as  possible. 
This  brings  rhythmical  pressure  against  the  portal  circulation  which 
is  also  of  great  additional  value  in  oxygenating  the  poisoned  blood  by 
giving  it  more  air  as  it  comes  to  the  lungs. 

But  to  obtain  permanent  results  it  is  necessary  to  do  more  than  this. 
The  abdominal  muscles  must  be  strengthened  for  they  have  lost  their 
tone.  This  means  that  they  must  be  exercised,  which  should  be  done 
gradually.  Frequently  lying  on  the  back  and  raising  the  head  a  little  is 
sufficient  to  strengthen  the  muscles  to  a  degree  that  will  permit  the 
raising  of  the  whole  body.  This  exercise  combined  with  raising  the 
feet  while  lying  on  the  back  will  bring  the  abdominal  tissues  again 
into  proper  tone.    It  is  well  to  remember,  however,  that  if  the  cure  is 


448         FRESH  AIR  AND  CORRECT  POSTURE 

to  be  lasting,  the  cause  must  be  entirely  overcome.  In  other  words, 
keep  erect. 

So  it  is  that  posture  connects  itself  very  distinctly  with  fresh  air. 
In  fact,  one  may  take  up  any  line  of  hygiene  and  find  that  it  extends 
in  its  importance  in  all  directions.  To  keep  well  it  is  necessary  not  only 
to  look  after  the  portal  circulation  and  proper  ventilation  of  rooms, 
but  also  the  diet.  The  teeth — the  instruments  with  which  to  handle 
the  diet — must  be  kept  clean,  and  like  all  organs  of  the  body,  given 
sufficient  exercise  to  keep  them  well. 

Truly  the  body  is  a  "harp  of  a  thousand  strings"  all  of  which  should 
be  kept  in  harmony.  This  chapter  deals  with  but  a  few  of  the  many 
strings,  but  to  put  and  keep  these  few  in  tone  will  help  to  set  all  of  the 
rest  in  harmonious  vibration. 


CHAPTER  XVII. 

LENGTHENING  THE  LIFE  OF  THE  RESISTIVE 
FORCES  OF  THE  BODY. 

By  WILLIAM   G.  ANDERSON,  M.D.,  Dr.P.H. 

The  resistive  forces  of  the  body  may  be  defined  as  nature's  defences 
against  harmful  agencies.  They  are  the  weapons  with  which  she  com- 
bats the  microorganisms  of  disease.  They  are  the  factors  that  are 
preeminently  concerned  in  maintaining  a  healthy  body. 

That  which  the  vast  majority  of  individuals  seek  most  is  happiness 
and  contentment.  It  is  well  to  remember,  therefore,  that  there  can 
be  no  complete  happiness  or  contentment  without  health.  The  pur- 
pose of  this  chapter  is  to  teach  those  things  that  will,  if  applied,  bring 
health. 

Long  ago  the  man  who  was  called  "the  master  of  those  who  know, 
the  private  secretary  of  nature,"  Aristotle,  the  Greek  philosopher, 
said :  "  The  highest  object  of  man  is  the  attainment  of  happiness,  and 
the  highest  happiness  of  man  is  to  be  reached  by  perfect  virtue. 
Neither  perfect  happiness  nor  perfect  virtue  can  be  had  without  per- 
fect health.  The  end  of  life,  and  therefore  the  end  of  education,  is 
the  attainment  at  once  of  intellectual,  moral  and  physical  virtue." 

The  element  of  interest  is  so  closely  associated  with  contentment 
that  the  modern  teacher  of  physical  training  is  adopting  methods  that 
appeal  strongly  to  his  pupils;  he  is  striving  to  make  bodily  develop- 
ment interesting. 

Sixty  years  ago  Herbert  Spencer  in  his  work  on  Education  referred 
to  the  failure  of  formal  gymnastics  to  accomplish  what  had  been  prom- 
ised in  its  name.  For  this  reason  he  preferred  the  plays  and  sports 
that  appealed  to  the  young  person.  Gymnastics  were  fundamentally 
defective,  formal  exercises  of  a  will-less  character  that  could  never 
supply  the  place  of  the  movements  prompted  by  nature.  There  is 
greater  benefit  in  the  riotous  glee  with  which  young  people  carry  on 
their  frolics.  Fictitious  exercise,  i.  e.,  gymnastics,  fail  to  give  the 
benefit  that  natural  spontaneous  activity  produces.  While  no  person 
can  lengthen  the  life  of  the  resistive  forces  of  the  body  who  does  not 
exercise  in  a  rational  manner,  yet  it  is  very  desirable  that  the  element 
of  interest  be  present.  Even  what  is  termed  "formal  gymnastics" 
become  less  irksome  if  associated  with  noticeable  bodily  improvement. 
Students  will  gladly  perform  the  "will-less  movements"  referred  to  if 
there  is  an  apparent  gain  in  poise,  balance,  grace,  strength  or  skill. 
29 


450    LENGTHENING   THE  LIFE  OF   THE   RESISTIVE  FORCES 

Young  men  and  women  forget  that  it  is  the  body  which  determines 
their  efficiency,  that  they  are  only  worth  what  the  body  will  permit 
them  to  do.  The  muscles  are  merely  instruments  which  act  in  accord- 
ance with  the  dictates  of  the  will  or  the  reflexes,  and  the  better  these 
instruments,  the  greater  the  good  that  can  be  accomplished.  This  is 
especially  true  in  the  case  of  those  who  have  been  well  educated 
intellectually. 

"It  is  more  or  less  clearly  recognized  that  no  skill,  no  learning,  no 
intellectual  greatness  can  carry  its  fullest  influence  without  a  certain 
element  of  physical  capacity  in  the  individual." 

The  reader  may  prove  an  apt  pupil  "but  the  terrible  earnestness 
of  the  race  of  life  is  not  best  met  by  mere  scholarship."  Horace  Mann 
said :  "  At  college  I  was  taught  the  motions  of  the  heavenly  bodies  as 
if  their  keeping  in  their  orbits  depended  upon  my  knowing  them, 
while  I  was  in  profound  ignorance  of  the  laws  of  health  of  my  own  body. 
The  rest  of  my  life  was,  in  consequence,  one  long  battle  with  exhausted 
energies."  There  is  abundance  of  evidence  of  this  character,  and  it 
comes  too  often  from  those  who  could  have  accomplished  more  if  they 
had  recognized  the  fact  that  there  is  no  act  of  life,  even  thinking,  that 
is  independent  of  the  body;  the  body  means  the  brain  and  the  neuro- 
muscular machinery  as  well  as  the  muscles.  A  mistaken  idea  prevails 
that  only  the  contractile  tissues  are  benefited  by  exercise.  The 
brain  substance  is  developed  by  voluntary  muscular  activity  as  are 
also  the  nervous  elements  connected  with  it. 

There  are,  roughly  speaking,  two  brains — one  for  movements,  the 
other  for  intellectual  activities.  These  are  closely  correlated,  are 
interdependent,  and  the  development  of  one  will  materially  assist 
when  the  other  is  to  be  trained. 

The  muscle  brain  is  called  the  motor  area,  the  Rolandic  division 
and,  like  its  sister  brain,  is  made  up  of  millions  of  cells.  Just  as  soon 
as  a  definite  circuit  can  be  made  among  the  cells,  and  energy  is  liber- 
ated, skilled  movement  is  the  result.  The  muscle  has  not  a  scintilla 
of  skill  in  itself,  it  is  merely  a  servant. 

The  greater  the  number  of  "circuits"  completed,  the  greater  the 
muscular  education  of  the  person  and  the  more  reliable  is  the  physical 
basis  of  psychic  activity.  Exercise  is  valuable  in  this  respect  because 
through  pleasurable  means  permanent  and  trustworthy  circuits  are 
built.  The  muscularly  versatile  man  possesses  good  brain  substance 
which  may  be  easily  trained  mentally,  but  like  gold  hidden  in  the 
ground,  it  is  valueless  unless  used.  The  majority  of  college  athletes 
stand  well  as  students,  many  of  them  receiving  honors. 

In  this  connection  it  is  well  to  discuss  what  is  called  "the  physical 
basis  of  psychic  activity"  or  the  development  of  the  brain  substance 
by  a  variety  of  voluntary  muscular  movements.  Making  the  directive 
centers  of  the  brain  skilful  in  muscular  evolutions  stimulates  and  assists 
the  faculties.  The  late  Professor  Angelo  Mosso  testifies  to  the  bene- 
ficial  reaction   ujxjn   the   mind   of  diversified   muscular  movements. 


LENGTHENING   THE  LIFE  OF   THE   RESISTIVE  FORCES    451 

Prof.  Mosso  cited  the  manual  activities  of  the  great  Itahan  masters 
as  in  point: 

"During  the  first  epoch  of  the  Renaissance  the  greatest  artists  of 
Florence  were  all  apprentices  in  the  workshops  of  goldsmiths.  Lucca 
Delia  Robbia,  Lorenzo  Ghiberti,  Fillipo  Brunelleschi,  Francia,  Ghir- 
landajo,  Botticelli,  Andrea  Del  Sarto — to  mention  only  a  few  examples — 
performed  during  their  apprenticeship  the  simplest  labors  in  the  work- 
shop of  a  goldsmith.  But  the  exercises  with  which  they  gained  their 
manual  dexterity  surely  influenced  also  the  development  of  their 
genius.  ...  A  fact  which  cannot  be  doubted  is  the  many-sided- 
ness of  genius  which  some  of  the  Italians  of  the  Renaissance  possessed, 
which  has  never  again  appeared  with  like  copiousness." 

The  games  and  dances  of  the  Greeks  also  must  have  assisted  in  the 
development  of  their  genius,  as,  on  the  other  hand,  their  intellectual 
exercises  affected  advantageously  the  development  of  the  muscles. 

The  reference  to  another  topic  that  is  closely  correlated  to  the  length- 
ening of  the  life  of  the  resistive  forces  of  the  body  may  create  as  much 
surprise  as  the  allusion  to  dancing  as  an  exercise.  This  is  grace.  Pro- 
fessor Layfayette  B.  IVIendel,  a  man  of  international  reputation  as  a 
physiologist,  once  said:  "Train  college  students  to  be  graceful.  It 
is  one  of  the  most  important  results  of  a  sensible  scheme  of  physical 
training.  The  graceful  man  husbands  his  physical  resources,  he  accom- 
plishes much  work  with  minimum  effort." 

Of  two  men  with  similar  personal  characteristics  who  perform,  one 
immediately  appeals  to  the  onlookers,  the  other  does  not;  one  receives 
hearty  applause,  the  other  fails,  and  we  ask  at  once,  why?  One  is 
graceful.  He  conserves  his  physical  energy,  he  spends  just  enough  to 
make  the  movements  accord  with  some  standard  that  exists  in  the 
human  mind.  The  other,  performing  the  same  evolutions,  wastes  his 
energy;  is,  in  short,  awkward. 

There  is  within  each  individual  a  harp  of  emotions  upon  which  chord 
of  harmony  or  dissonance  are  struck  by  graceful  or  awkward  move- 
ments. Precisely  what  this  harp  is,  is  not  known;  only  a  long  and  care- 
ful study  of  rhythm  and  harmony  will  answer  the  question.  It  is  cer- 
tainly there,  and  men  are  made  either  happy  or  distressed  by  the  feel- 
ings that  motion  arouses. 

Again  it  is  well  to  emphasize  the  fact  that  the  development  of  the 
muscles  and  the  neuromuscular  machinery  is  not  the  sum  total  of 
physical  education.  There  are  many  who  cannot  become  graceful 
or  who  find  they  are  unable  to  acquire  the  poise  and  balance  so  neces- 
sary to  complete  bodily  living,  but  they  can  at  least  keep  in  better 
condition  the  protective  forces  of  the  human  mechanism  by  taking 
exercises  and  by  living  a  hygienic  life. 

It  is  such  a  satisfying  bit  of  information  to  know  that  if  one  is  not 
able  to  acquire  the  beautiful  physiques  of  the  male  or  female  gods  he 
can  at  least  add  to  his  contentment  and  health  by  rational  physical 
activity  plus  right  living. 


452    LENGTHENING   THE  LIFE  OF   THE   RESISTIVE  FORCES 

]\Ian's  enemies  are  infinitesimal,  they  are  the  germs  which  generate 
poisons  in  the  body,  and  the  bulwark  erected  by  nature  against  these 
attacking  forces  is  made  up  of  builders  and  fighters  which  are  also 
microscopic,  the  red  and  white  blood  corpuscles.  Health  depends 
upon  the  vitality  of  the  tiny  elements  which  constitute  the  protection 
against  poisons,  and  it  is  perfectly  possible  to  either  strengthen  or 
weaken  these  blood  cells  by  methods  of  living.  These  guardians 
are  reinforced  by  careful  living,  by  rest,  by  rational  and  pleasing  forms 
of  bodily  activity,  hence  the  need  of  attention  to  hygiene  and  sanita- 
tion, to  the  observance  of  the  laws  of  health,  to  exercise. 

The  forms  of  g\Timastics  that  stimulate  the  action  of  the  heart  and 
lungs  and  the  movements  that  wash  out  the  organs  and  tissues  of  the 
body  with  fresh  arterial  blood  go  far  toward  the  development  and 
growth  of  healthy  tissue  cells;  consequently  the  necessity  for  a  cer- 
tain amount  of  daily  muscle  activity.  It  is  a  mistake  to  suppose 
that  a  person  must  take  violent  or  prolonged  exercise. '  A  very  few 
minutes  at  a  time  will  suffice.  It  is  a  mistake  to  think  that  a  gym- 
nasium is  needed.  A  goodly  part  of  the  right  kind  of  physical  training 
can  be  taken  in  the  sleeping-room,  at  the  place  of  business,  or  on  the 
street. 

The  most  important  kind  of  gymnastics  is  assuming  and  maintain- 
ing a  correct  standing  or  sitting  position.  In  this  case  the  many  mus- 
cular groups  of  the  body  are  brought  into  action.  But  little  time  is 
required  and  the  desirable  habit  is  soon  formed.  No  apparatus 
is  needed  except  the  edge  of  a  door  against  which  one  should  stand 
several  times  a  day.  The  posture  may  not  be  exactly  ideal  but  it 
stimulates,  and  in  a  short  time  this  straight  door  edge  may  be  dispensed 
with. 

Another  very  important  factor  in  the  development  of  the  physical 
basis  of  psychic  activity  is  the  care  of  the  five  roads  over  which  sensa- 
tions travel  to  the  brain.  These  roads  are  known  as  the  senses.  Hear- 
ing, seeing,  feeling,  tasting,  smelling  are  improved  if  the  machinery 
is  kept  in  good  condition. 

The  life  of  the  resistive  forces  of  the  body  are  prolonged  if  the  exposed 
mucous  membranes  of  the  bod}^  are  often  well  supplied  with  fresh 
arterial  blood,  and  rational  exercise  does  this.  Movements  of  the  neck 
send  the  fluid  tissue  not  only  to  the  muscles  but  also  to  all  adjacent 
areas,  hence  there  is  a  building  up  of  minute  bodily  substances  in  the 
eyes,  the  mouth,  the  ears,  the  nose,  and  the  little  builders  and  fighters 
are  on  duty  to  repair,  or  combat  poisonous  germs  if  they  are  present. 

This  is  the  crux  of  the  whole  ^liscussion,  as  it  will  be  at  once  seen 
tiiat  trvMik  movements  will  do  the  same  for  the  contents  of  the  abdom- 
inal cavity,  and  active  leg  work  which  stimulates  the  action  of  the 
heart  and  lungs  will  in  a  like  manner  i)rotect  and  strengthen  the  car- 
diac and  pulmonary  machinery. 

As  the  subject  is  too  large  to  be  easily  handled  in  a  satisfactory  man- 
ner in  one  chapter,  the  standing  position  and  the  development  of  the 


HOW   TO  STAND   WELL  453 

thorax,  or  chest  as  it  is  often  called,  will  be  selected  for  treatment, 
and  from  this  the  student  may  evolve  ideas  that  may  be  applied  to 
other  portions  of  the  body.  A  good  standing  ])osition  means  an  arched 
chest,  shonlders  well  placed,  abdomen  brought  in,  head  erect  and  the 
whole  body  properly  poised  or  balanced  over  the  feet  and  legs. 

HOW   TO    STAND   WELL. 

The  erect  posture  is  the  normal  pose  of  man  alone;  no  other  animal 
has  this  prerogative.  It  is  therefore  essential  that  we  cultivate  the 
vertical  axis  of  the  spine,  insist  upon  our  pupils'  standing  well,  and 
teach  exercises  that  will  produce  this  result.  Any  deviation  from  the 
normal  position  will  bring  abnormal  consequences,  slight  variations 
from  the  healthy  condition  of  man. 

The  right  idea  of  the  standing  position,  coupled  with  will  power, 
are  essential  factors  needed  in  producing  an  erect  posture.  The  gym- 
nasium with  its  apparatus  is  unnecessary.  Anyone  may,  many  times 
each  day,  assume  and  maintain  an  erect  carriage.  In  a  very  few  weeks 
the  entire  contour  of  the  body  will  change,  and  the  improvement  is 
not  only  esthetic  but  hygienic. 

Should  the  reader  wish  to  examine  a  careful  work  on  the  correct 
standing  position,  let  him  read  The  Kinesiology  of  the  Trunk,  Shoulder, 
and  Hip  Ayplied  to  Gymnastics,  by  William  Skarstrom,  M.D.,  of 
Wellesley  College. 

A  well-known  orthopedic  surgeon  has  popularized  the  "erect-pos- 
ture idea"  by  stating  that  in  a  way  the  various  organs  of  the  body  are 
supported  on  shelves  when  the  body  is  rightly  carried,  but  as  soon  as 
the  body  is  bent  or  habitually  inclined  the  organs  slip  from  their 
supports,  and  bring  additional  work  to  other  structures  that  are  already 
burdened  with  their  own  duties. 

Dr.  Joel  Goldthwait,  of  Boston,  in  his  paper  read  before  the  American 
Physical  Education  Association  in  Philadelphia,  April  9,  1909,  said: 

"  It  should  next  be  remembered  that  the  pelvis  represents  the  struc- 
tiu'al  base  of  the  body,  that  all  of  the  trunk  muscles  are  attached  to  it, 
that  practically  all  of  the  thigh  muscles  are  also  attached  to  it,  and 
that  if  for  any  reason  the  structural  base  is  weak,  the  muscles  that  are 
attached  to  it,  since  they  cannot  act  normally,  must  become  weak. 
This  means  that  it  is  useless  to  expect  the  muscles  to  regain  their 
proper  tone  if  the  base  to  which  they  are  attached  is  weak. 

"Not  only  this,  but  it  is  unfair  to  expect  that  the  body  will  be  held 
in  proper  poise  or  used  with  normal  freedom  if  the  pelvis  is  weak,  since 
the  muscles  cannot  have  their  proper  tone  and  the  correct  position 
must  be  difficult,  if  not  impossible,  to  maintain.  Not  only  is  the  proper 
tone  of  the  pelvic  joints  of  importance  in  maintaining  the  poise  of  the 
body,  but  if  for  any  reason  the  correct  poise  is  impossible,  it  means 
that  not  only  is  the  posture  imperfect,  but  that  the  viscera  will  be  less 
well  supported  and  their  function  less  perfectly  carried  on.     If  the 


454    LENGTHENING   THE  LIFE  OF   THE   RESISTIVE  FORCES 


V 


'H 


I 


body  is  erect,  the  abdominal  viscera  are  held  in  place  by  the  muscles 
and  by  certain  anatomical  supports  which  lose  their  effect  when  the 

body  droops,  and  it  is  because  of 
this  that  many  of  the  displacements 
of  the  viscera  take  place. 

"Not  only  is  this  true,  but  if 
for  any  reason  the  erect  posture  is 
impossible,  the  spinal  muscles  be- 
come still  further  weakened  as  the 
result  of  the  strain  which  must  be 
thrown  upon  them,  and  with  this 
weakening  of  the  muscles  about  the 
spine  the  circulation  in  the  spinal 
cord  must  also  be  interfered  with 
— a  fact  which  explains  many  of  the 
nervous  phenomena  seen  in  such 
cases." 

On  this  point  Huxley  says,  in  his 
Physiology:  "But  man  possesses 
certain  special  or  distinctive  ana- 
tomical characters.  The  most  notice- 
able, as  seen  on  an  external  inspec- 
tion of  his  body,  is  his  erect  posi- 
tion. He  is,  indeed,  the  only  liv- 
ing creature  that  can  walk  or  stand 
erect,  i.  e.,  with  the  axis  of  the  spine 
vertical;  with  the  hip  and  knee- 
joints  capable  of  being  fully  ex- 
tended, so  that  the  leg  is  brought 
into  line  with  the  thigh;  with  the 
foot  so  planted  on  the  ground  that 
it  rests  on  the  heel  behind  and  on  the 
roots  of  the  toes  in  front;  with  the 
upper  limbs  so  arranged  as  to  act, 
not  as  instruments  of  progression, 
but  of  prehension;  and  with  the 
head  so  balanced  on  the  top  of  the 
spine  that  the  face  and  eyes  look 
directly  to  the  front.  His  bones, 
joints,  and  muscles  are  constructed 
and  arranged  so  as  to  enable  him 
to  preserve  the  erect  attitude  without  fatigue.  In  other  vertebrata 
the  axis  of  the  spine  is  oblique  or  horizontal;  the  hip-  and  knee-joints 
are  permanently  bent  at  a  more  or  less  acute  angle;  the  limbs  corre- 
sponding to  the  human  u])per  extremities  are,  in  the  form  of  legs,  wings, 
or  fins,  instruments  of  progression;  and  the  head  is  articulated  with 
the  spine  at  or  near  the  hinder  end  of  the  skull."    (See  Fig.  218.) 


Fig.  218. — A  diagram  illustrating  the 
attachments  of  some  of  the  most  im- 
portant muscles  which  keep  the  body 
in  the  erect  posture.  /,  the  muscles  of 
the  calf;  II,  those  of  the  back  of  the 
thigh;  III,  those  of  the  spine.  These 
tend  to  keep  the  body  from  falling  for- 
ward. 1,  the  muscles  of  the  front  of 
the  leg;  2,  those  of  the  front  of  the 
thigh ;  3,  those  of  the  front  of  the  ab- 
domen -,4,  5,  those  of  the  front  of  the 
neck.  These  tend  to  keep  the  body 
from  falling  backward.  The  arrows 
indicate  the  direction  of  action  of  the 
muscles,  the  foot  being  fixed.  (From 
Huxley's  Physiology.) 


HOW   TO  STAND   WELL 


455 


Fig.  219.— Defect.  Right  shoulder 
lower  than  the  left,  caused  by  over- 
development of  the  right  side. 


Fig.  220. — Shows  uneven  shoulders  and 
a  lateral  curve  in  the  spine  caused  by 
resting  the  weight  of  the  body  on  one  leg. 


Fig.  221. — Projecting  hips. 


Fig.  222. — Side  view  of  a  well-built  boy. 


456    LENGTHENING   THE  LIFE  OF   THE   RESISTIVE  FORCES 

The  foregoing  may  seem  too  technical,  but  it  is  written  for  those 
who  are  competent  to  teach  others;  it  is  not  for  the  boy  or  the  girl. 
A  glance  at  the  pictures  will  give  a  better  idea  of  some  of  the  variations 
in  the  standing  position. 

The  following  are  simple  rules  for  developing  and  maintaining  the 
erect  standing  position. 

Bring  the  heels  and  knees  close  together.  If  the  conformation  of 
the  body  prevents  either,  then  bring  them  as  close  together  as  possible. 
Carry  the  hips  well  back  and  the  chest  forward.  The  shoulders  should 
be  level,  the  arms  hanging  naturally  at  the  side  but  somewhat  back. 

The  head  should  be  erect,  the  chin  slightly  drawn  in,  and  the  eyes  to 
the  front  or  slightlv  raised. 


fj 


Fig.  224. — Diagram  of  the  displacement  of  the 
ribs  and   sternum  in  inspiration,     a  indicates   the 
Fig.    223.  —  Drooping    head  degree  of  upward  movement;     b,  that  of  forward 

and  flat  chest.  movement.     (Testut.) 

The  entire  weight  of  the  body  should  be  well  forward  on  the  balls 
of  the  feet,  not  back  on  the  heels.     (See  Fig.  222.) 

Press  the  back  of  the  neck  against  the  collar. 

Do  not  tilt  the  head  backward. 

Jf  a  large  looking-glass  is  available,  stand  before  this  in  the  above 
position  several  times  a  day  for  only  sixty  seconds  at  a  time. 

Stand  against  the  edge  of  the  door  three  times  a  day  for  only  one 
minute  at  a  time,  assuming  the  position  above  outlined. 

Place  in  your  looking-glass,  or  on  your  table,  a  card  or  some  special 
object  which  will  remind  you  to  stand  well.  When  the  object  is  no 
longer  effective,  change  it. 

Train  yourself  to  thi?ik  of  standing  well. 


THE  DEVELOPMENT  OF   THE  CHEST 


457 


THE   DEVELOPMENT    OF    THE   CHEST. 

Too  much  attention  cannot  be  given  to  tlie  development  of  the 
"bony-cartilaginous  cage  that  contains  the  heart  and  lungs."  The 
widening  and  deei)ening  of  the  "chest"  is  of  vital  importance,  for  here 
we  find  the  never-ceasing  pump  and  the  machinery  for  the  ventilation 
of  the  blood. 

It  was  shown,  when  speaking  of  the  standing  position,  that  the 
erector  spince  group  of  muscles  (back  muscles)  do  much  to  maintain 
the  erect  posture.  It  is  equally  true  that  these  same  muscles  are 
most  active  in  arching  the  thorax,  in  raising  the  ribs. 


Fig.  225. — Bent-arm  position. 


Fig.  226. — Stretch  position,  arms  up. 


This  brief  recital  presents  the  principles  that  should  govern  us  in 
the  selection  of  exercises  to  correct  flat  chest,  funnel-  and  pigeon-breast, 
and  other  forms  of  thoracic  asymmetry. 

1.  Arch  the  thorax  by  the  contraction  of  the  back  muscles. 

2.  Elevate  the  ribs  by  raising  the  arms  above  the  head.    (Fig.  226.) 

3.  Increase  the  capacity  of  the  lungs  by  deep  breathing  and  by  active 
leg  work,  running,  rope-skipping,  etc. 

4.  Develop  the  heart  by  active  leg  work. 

The  above  simple  principles  may  be  condensed  into  one  general  law, 
i.  e.,  to  widen  and  deepen  the  thorax,  raise  the  ribs. 

Movements  of  the  ribs  and  the  thorax  as  a  whole.  When  breathing 
in,  the  thorax  is  enlarged  in  its  three  diameters — transverse,  through, 


458    LENGTHENING   THE  LIFE  OF   THE   RESISTIVE  FORCES 

and  vertical.  The  increase  in  the  vertical  diameter  is  caused  partly  by 
the  elevation  of  the  upper  ribs,  and  the  resulting  widening  of  the 
spaces  between  the  ribs,  but  is  mainly  due  to  the  action  of  the  dia- 
phragm. The  increase  in  the  other  two  directions  is  due  to  the 
movements  of  the  ribs,  which  are  greatest  where  the  ribs  are  longest, 
most  oblique,  and  most  curved  at  their  angles  (^.  e.,  at  the  sixth, 
seventh,  and  eighth  ribs  opposite  the  bulkiest  part  of  the  lungs),  and 
least  in  the  short,  flat  first  and  second  ribs. 

The  above  change  in  the  thoracic  diameters  is  brought  about  by 
the  movements  seen  in  Figs.  225  and  226. 


CHAPTER  XVIII. 

THE  TEACHING  OF  :\IOUTH  HYGIENE  TO 
SCHOOL  CHILDl^EN. 

By  THADDEUS   P.  HYATT,  D.D.S. 

Almost  anything  is  easy  to  follow  if  a  few  fundamental  facts  or 
truths  are  grasj^ed,  and  work  with  children  is  no  exception.  Children 
are  intuitive.  Intuition  in  children  controls  and  guides  their  emotions 
and  feelings.  These  emotions  and  feelings  are  not  formed  into  words 
or  intellectual  sentences,  but  are  sensed  tlirough  intuition.  They 
know  their  relation  toward  others  by  their  intuitive  faculty  and 
not  by  their  intellectual  development.  Children  are  very  simple. 
They  rarely  have  affectation.  They  go  direct  to  the  subject  and  do  not 
"beat  about  the  bush"  before  coming  to  the  point.  Consequently 
the  attitude  taken  by  adults  toward  children  must  be  absolutely  free 
from  pretence.  It  is  of  no  use  to  pretend  to  love  a  child,  for  it  will  not 
be  deceived.  Love  for  children  is  a  necessary  requisite  in  handling 
children  and  this  can  be  developed.  Every  human  being  is  capable 
of  developing  love  and  affection.  All  that  is  beautiful  in  humanity 
is  represented  in  the  child.  It  is  not  yet  contaminated  by  the  mate- 
rialism of  the  world. 

Our  attitude  must  always  be  that  of  being  at  oneness  with  the  child. 
In  addressing  children  it  is  necessary  to  talk  with  them,  not  to  or  at 
them.  Include  them  with  yourself.  This  inclusiveness  must  be  real. 
The  feeling  must  be  one  of  inward  reality.  They  will  listen,  and  the 
feeling  of  inclusiveness  will  enable  them  to  understand.  Children 
grasp  truths  with  the  intuitive  faculty  or  subjective  nature  which  is 
in  sympathy  with  the  intuitive  or  subjective  side  of  the  adult.  They 
will  imderstand  by  their  inner  consciousness  or  subjective  self-responfl- 
ing  to,  and  receiving  their  impressions  from,  the  subjective  side  of  the 
adult. 

Sometimes  the  child  will  be  timid  or  afraid,  and  this  is  generally 
the  result  of  his  being  unaccustomed  to  the  strange  new  presence; 
and  he  must  not  be  forced  to  make  an  outward  expression  when  his 
inward  consciousness  is  working  on  the  newness  of  the  personality 
which  he  has  met.  It  is  best  to  ignore  him,  for  if  attention  be  paid  to 
him,  his  consciousness  becomes  confused  and  the  child  is  injured. 

As  illustration,  a  mother  brought  two  little  sisters  to  the  dentist's 
office.  One  became  friendly  at  once,  willingly  ran  into  the  operating 
room  and  jimiped  up  into  the  chair.  The  dentist  was  able  to  work  on 
her  without  difficulty.    But  the  other  child,  keenly  aware  of  the  strange- 


460    TEACHING  OF  MOUTH  HYGIENE  TO  SCHOOL  CHILDREN 

ness  of  the  surroundings  and  the  dentist,  threw  herself  down  on  the 
floor,  rolled  and  kicked  and  screamed.  The  dentist  did  not  try  to. soothe 
her  or  to  talk  with  her,  but  ignored  her,  going  on  Avith  his  work  on  the 
other  child.  Later  the  mother  was  asked  to  bring  her  with  her  sister 
the  next  time  and  leaA'e  her  with  the  dentist  but  not  to  make  any 
comments  from  one  appointment  to  the  next.  The  child,  thinking  the 
dentist  intended  putting  her  into  the  chair  went  into  a  temper  and 
kicked  and  screamed  again.  Again  she  was  ignored,  the  dentist  leaving 
her  entirely  alone  and  going  on  with  the  work  for  the  sister.  Finally,  as 
the  strangeness  wore  ofT,  she  went  over  and  stood  by  the  chair,  watch- 
ing the  work  and  looking  at  the  dentist,  which  was  what  she  wanted 
to  do  all  the  time,  in  order  to  become  acquainted  with  the  situation. 
She  had  thought  she  would  be  forced  to  get  into  the  chair  and  when 
she  found  such  was  not  the  case,  and  that  she  was  not  even  asked  to, 
she  began  to  adjust  and  understand  her  own  feelings  toward  the  den- 
tist, and  when  at  the  third  or  fourth  visit  to  the  office  he  did  ask  her  to 
get  into  the  chair,  she  did  it  willingly  and  eagerly,  after  which  all  rela- 
tions between  her  and  the  dentist  were  easy  and  happy.  The  morale 
of  this  illustration  is  that  the  undefined  feeling  for  a  new  and  strange 
personalit}'  must  be  respected  and  not  suppressed.  Another  point 
of  importance  is  the  realizing  of  the  child's  equality  with  the  teacher, 
and  this  is  dependent  upon  two  things.  First,  the  absolute  right  of 
the  child  to  have  the  truth,  and  nothing  but  the  truth,  told  him  in  rela- 
tion to  the  particular  subject  dealt  with;  and  second,  the  child's 
right  to  be  treated  as  a  human  being,  as  a  member  of  the  human  family, 
and  not  as  a  little  puppy  or  kitten.  Children  are  human  beings  and 
they  feel  resentment  at  once  if  they  are  treated  in  any  other  relation 
whatsoever.  They  have  ability  to  know  and  to  understand  through 
their  intuitive  side.  It  is  folly  to  try  to  deceive  them,  for  their  intuition 
would  tell  them  the  truth  in  spite  of  deception. 

Having  established  relations  with  children  along  these  lines,  the 
subject  of  how  to  address  them  must  be  considered.  If  methods 
based  on  the  principles  suggested  are  carried  out,  it  will  be  found  impos- 
sible to  talk  over  the  children's  heads.  The  faults  of  the  methods 
employed  when  it  is  said  that  someone  "talked  over  the  children's 
heads,"  or  "the  subject  was  too  deep  for  the  children"  or  "it  was 
beyond  their  comprehension  and  understanding,"  lies  with  the  person 
giving  the  address  or  talk,  and  not  with  the  children.  The  child's 
mind  goes  direct.  It  travels  in  a  straight  line  to  the  object.  It  is 
simple  and  needs  very  definite  language  to  enable  it  to  understand 
the  subject  under  discussion.  Adults  who  have  perhaps  gone  beyond 
that  stage  of  development  are  apt  to  use  with  children  the  language 
they  might  use  with  one  another.  Instead,  language  must  be  used 
that  will  go  straight  to  the  subject,  with  the  fewest  and  simplest  words. 
This  knack  can  be  ac(]uircd  if  it  does  not  come  naturally  to  the  teacher, 
by  study,  by  listening  to  those  who  have  the  ability  of  talking  to  chil- 
dren, and  by  writing.    A  good  exercise  in  writing,  where  the  words  can 


TEACHING  OF  MOUTH  HYGIENE  TO  SCHOOL  CHILDREN   461 

be  seen,  is  to  discard  and  rei)lace  complex  words  with  simple  ones. 
When  simplicity  has  been  acquired  the  teacher  will  find  scarcely  any- 
thing the  child  is  miable  to  understand.  As  an  illustration:  a  little  girl 
of  four  and  a  half  years  of  age  had  become  so  absorbed  in  play  she  did 
not  notice  that  the  day  had  grown  dark.  Suddenly  she  went  to  the 
window  and  noticing  the  change  she  said,  "The  day  is  dark,  the  light 
has  all  gone  out  of  it."  What  could  be  more  simply  expressed,  yet  so 
truthful,  direct  and  clear?  Anyone  could  understand  it.  It  is  even 
poetic  in  its  simplicity.  This  is  what  is  needed  in  talking  with 
children — language  that  is  simple  yet  clear  and  definite  in  expression. 

Diu'ing  the  activity  of  the  intuitive  and  subjective  nature  of  the 
child,  it  has  no  relation  to  or  with  the  intellectual.  Therefore  those 
ideas  or  things  which  are  to  be  appreciated  or  apprehended  must  be 
very  definite  in  character  and  clear  in  formation.  The  child  must  have 
definite  word  pictures.  No  cubist  or  impressionist  school  can  satisfy 
the  child  in  the  world  of  words. 

It  is  imi)ortant,  too,  to  know  the  environment  of  a  child.  Not  so 
much  as  to  whether  it  has  been  brought  up  in  luxury  or  poverty,  as 
to  whether  it  has  been  so  placed  as  to  need  to  use  and  exercise  its  own 
intelligence  and  direct  its  own  activities,  or  whether  it  has  been  pam- 
pered and  accustomed  to  have  others  do  things  for  it.  It  is  of  course 
harder  to  work  or  talk  with  children  that  have  been  pampered  than 
with  those  who  have  some  self-reliance. 

Children  are  best  taught  by  means  of  stories.  A  good  plan  is  for 
the  teacher  to  write  out  in  story  form  what  is  to  be  taught  the  child, 
re^\Titing  and  revising  it  until  it  is  simple,  direct  and  definite,  always 
keeping  in  mind  the  definiteness  of  the  idea  and  the  simplicity  of  form. 
Stories  may  be  told  about  animals'  teeth,  their  size  and  shape  and 
their  several  uses,  and  about  the  teeth  of  the  children  themselves,  and 
why  they  are  shaped  differently  in  different  parts  of  their  mouth  each 
to  do  its  particular  kind  of  work.  Children  are  eager  to  learn.  Nothing 
is  so  interesting  to  them  as  making  discoveries.  Therefore  the  bringing 
of  a  new  idea  to  them  in  a  way  they  can  assimilate  it,  is  interesting  to 
them.  If  the  subject  is  interesting,  they  will  grasp  it  and  absorb  it. 
Kipling's  "Just-So"  stories  are  good  examples  for  study,  as  they  are 
definitely  and  simply  told.  If  the  form  of  these  stories  is  adopted  in 
telling  stories  to  children,  their  interest  will  be  held  through  to  the  end. 

It  is  important  that  the  children  learn  to  express  themselves,  for 
they  grow  through  expression.  After  some  information  has  been  given 
to  them  they  should  have  time  to  absorb  and  digest  it  and  to  show 
that  they  have  grasped  and  understood  it,  and  then  be  asked  to  express 
themselves  outwardly  in  some  wa.y.  They  should  be  encouraged  in 
passing  on  the  information  to  some  of  their  friends.  In  their  manner 
of  teaching  other  children  will  be  found  valuable  suggestions  for  the 
adult  teacher.  Children  are  efficient  teachers  and  much  can  be  learned 
from  them. 

The  teacher  must  learn  to  act  as  interpreter,  helping  the  children  to 


462    TEACHING  OF  MOUTH  HYGIENE  TO  SCHOOL  CHILDREN 

understand  things,  material  facts.  An  interpreter  deals,  not  with 
theories,  but  with  facts,  directing  attention  and  aiding  understanding. 
The  meaning  of  certain  facts  is  interpreted  to  the  child,  he  understands 
and  acts  accordingly,  and  thereafter  is  in  the  same  relation  to  the  facts 
as  the  interpreter  or  teacher.  All  of  this  will  be  appreciated  by  the 
child  and  creates  a  bond  between  him  and  the  teacher  and  develops 
a  sense  of  loyalty.  He  then  has  a  responsibility  and  a  duty  to  per- 
form and  will  do  what  is  being  taught  him,  not  just  because  he  is  told 
to,  but  because  he  has  learned  why.  Thus  children  will  not  brush  their 
teeth  because  they  are  told  to,  but  will  do  so  acting  independently 
and  because  of  their  own  knowledge  and  belief.  They  will  realize  the 
natural  relation  to  the  laws  of  nature  which  have  been  interpreted  to 
them,  and  clean  their  mouths  of  their  own  volition,  their  own  under- 
standing. 

It  is  hard  always  to  take  the  positive  attitude  with  children,  yet 
it  is  the  positive  that  educates.  The  negative  form  has  no  value.  It 
is  said  that  the  commandment  "Thou  shalt  not  steal"  has  made  more 
thieves  than  anything  ever  written,  for  the  "shalt  not"  being  negative 
entirely  disappears,  and  "steal,"  which  is  positive,  is  the  idea  left.  It 
is  the  positive  which  is  impressed  upon  the  mind.  "Be  good,"  is  a 
positive  statement  and  will  have  value.  "Do  not  be  bad,"  will  have 
the  opposite  effect,  tending  toward  badness  as  the  idea  left  in  the 
mind.  Therefore,  in  dealing  with  children,  every  subject  should  be 
presented  in  the  positive  form. 

While  children  are  quick  in  their  assimilation  of  intuitive  knowledge 
they  are  exceedingly  slow  in  the  acquisition  of  physical  facts.  It 
will  take  them  considerable  time  to  know  how  to  brush  the  teeth 
correctly,  because  they  have  not  only  to  perform  the  act,  not  only 
to  think  of  it,  but  have  also  to  fix  the  impression.  As  in  photography 
there  is  what  is  known  as  a  fixing  solution  in  which  it  takes  time  to 
fix  the  photograph,  and  which  process  cannot  be  hurried,  so  with  the 
children — they  need  to  have  plenty  of  time  to  fix  the  impression  and 
they  should  be  given  all  the  time  they  need.  They  are  slow,  neces- 
sarily, because  there  are  no  short  routes  in  fixing  impressions  on  the 
child's  mind. 


CHAPTER   XIX; 
INSTITUTIONAL  DENTISTRY. 

FOREWORD  BY  A.  C.  FONES,  D.D.S. 

Although  there  may  be  other  reports  concerning  institutional  work 
previous  to  that  of  Dr.  J.  F.  Havestardt,  of  Boston,  it  is  one  of  the 
earHest  bearing  on  the  eHmination  of  the  infectious  diseases  of  child- 
hood through  mouth  hygiene. 

The  report  in  full  may  be  found  in  the  Dental  Cosmos  for  January, 
1905.  In  the  Poor  Children's  Home  in  West  Roxbury,  jVIassachusetts, 
there  were  about  sixty  children  varying  in  age  from  two  to  fourteen 
years.  None  of  these  children  ever  had  dental  service  and  were  obliged 
to  live  through  the  pain  of  exposed  pulps  and  abscessed  teeth.  The 
institution  was  too  poor  to  pay  for  such  service,  although  it  did  employ 
a  physician  and  buy  drugs  when  necessary. 

Dr.  Hovestardt,  moved  to  pity  over  the  situation,  attempted  to 
cope  with  the  awful  mouth  conditions  he  found  there  and  gave  one 
morning  a  w^eek  for  several  years  until  he  secured  clean  mouths  and 
sound  teeth.  In  a  part  of  his  report  he  says,  "In  former  years  diphth- 
eria and  many  other  diseases  have  been  prevalent  at  the  Home,  but 
for  some  time  past  not  a  single  disease  of  the  kind  has  been  reported. 
In  keeping  the  mouths  of  these  children  comparatively  clean,  and  as 
free  as  possible  from  microorganisms,  we  greatly  assist  nature  in  her 
work,  increasing  the  power  of  resistance  to  a  large  extent."  The 
following  is  a   letter   to   Dr.  Hovestardt   from   the   superintendent, 

Rev.  F.  Wilhelm: 

"West  Roxbury,  April  3,  1904. 
Dear  Doctor: 

If  the  enclosed  record  is  of  any  use  to  you,  I  shall  be  pleased  at  any 
time  to  vouch  for  the  correctness  of  the  following  statement  or  record : 

Since  the  time  you  have  taken  care  of  the  children's  teeth  in  our  insti- 
tution, the  health  record  has  been  remarkably  improved.  There  has 
been  no  more  typhoid  or  diphtheria.  For  this  we  have  to  thank,  in  the 
first  place,  God,  but  it  is  also  due  to  the  scientific  and  conscientious 
work  you  have  done  for  the  children.  The  doctor's  and  drug-store 
expenses  for  the  past  nine  years  have  been  as  follows: 

1895 S89.97 

1896 70.94 

1897 49.78 

1898 45.61 

1899 303.39 

1900 38.29 

1901 2.88 

1902 3.80 

1903 ....  8.86 


464  INSTITUTIONAL  DENTISTRY 

The  reason  that  the  expenses  were  so  much  higher  in  1899  than  in 
the  preceding  years  was  due  to  the  fact  that  two  newly  arrived  chil- 
dren had  brought  the  measles  and  whooping-cough  into  the  insti- 
tution, and  eighteen  children  were  affected  by  the  same.  The  sum 
includes  pay  for  nurse.  The  great  decrease  in  physician's  and  drug 
expenses  is  most  markedly  shown  by  the  last  three  years,  as  the  same 
have  been  reduced  from  $89.97  in  1895  to  $2.88  in  1901,  $3.80  in  1902 
and  $8.86  in  1903.  Rev.  F.  Wilhelm,  Supt." 

A  similar  demonstration  but  one  more  impressive,  because  it  involves 
a  larger  number  of  children,  was  made  by  Dr.  Frederick  A.  Keyes, 
D.M.D.,  of  Boston,  at  the  St.  Vincent's  Orphan  Asylum  in  Boston. 
Although  he  has  been  opposed  to  all  dental  nurse  legislation  as  pre- 
sented in  Massachusetts  up  to  the  present  time,  yet  his  work  and  writ- 
ings show  that  he  is  keenly  interested  in  mouth  hygiene.  Many  have 
different  points  of  view  as  to  how  this  problem  should  best  be  solved. 
Time  alone  will  show  which  is  the  better  plan.  A  full  detail  of  his 
work  at  St.  Vincent's  Orphan  Asylum  may  be  found  in  the  Boston 
Medical  and  Surgical  Journal  for  July  25,  1912,  and  January  15,  1914: 

INSTITUTIONAL   DENTISTRY  VERSUS   INFECTIOUS   DISEASES 
OF   CHILDHOOD. 

By  FREDERICK  A.  KEYES,  D.M.D. 

All  the  great  medical  discoveries  of  the  past  decade  have  existed 
for  centuries  in  the  minds  of  theorists  and  dreamers.  The  fundamental 
principles  involved  are  centuries  old.  The  scientific  and  practical 
application  of  these  principles  for  the  benefit  of  mankind  belongs  to 
this  generation.  The  relation  of  mouth  hygiene  to  the  infectious 
diseases,  especially  of  childhood,  seemingly  the  most  demonstrable 
of  all  pathological  etiologies,  has  been  the  last  to  receive  the  recog- 
nition which  its  importance  has  warranted.  Dentists  have  been  clam- 
oring for  years  for  cooperation  from  the  medical  profession  in  the 
elimination  of  disease.  They  have  taken  for  granted  the  importance 
of  their  field  of  endeavor,  and  have  been  theorizing  and  proving  by 
logical  deductions  the  many  diseases  that  might  possibly  be  traced  to 
unsanitary  mouths. 

During  this  period  of  complacency  and  theorizing,  however,  other 
I)rofessions  have  been  experimenting  and  ])resenting  facts  to  prove 
their  theories.  This  is  a  scientific  age.  To  prove  the  importance  of 
any  set  of  theories  or  opinions  the  facts  must  be  at  hand.  To  prove, 
therefore,  to  his  own  satisfaction  that  the  truth  of  these  theories  so 
enthusiastically  stated  and  upheld  by  his  predecessors  and  contem- 
poraries in  the  dental  profession  was  warranted,  the  writer  obtained 
permission  to  do  dental  work  at  St.  Vincent's  Orphan  Asylum,  Boston. 
Work  was  begun  Nov.  10,  1910.     In  reviewing  dental  literature  of 


INSTITUTIONAL  DENTISTRY  465 

the  last  fifteen  years,  very  little  information  was  found,  bearing  upon 
the  methods  prevalent  in  institutional  dentistry,  due  to  the  fact  that 
institutional  dentistry  in  this  country  is  a  rarity.  Although  there  may 
be  defects  in  the  system  at  present  in  vogue  at  St.  Vincent's,  neverthe- 
less the  writer  has  presented  to  the  medical  and  dental  professions 
two  articles  bearing  on  this  subject  through  the  medium  of  the  Boston 
Medical  and  Surgical  Journal.  The  methods  employed  in  doing  this 
work  are  described  in  the  above  articles.  The  results  obtained  from 
having  this  work  done  and  its  relation  to  infectious  diseases  of  child- 
hood are  presented  below. 

St.  Vincent's  Orphan  Asylum  is  the  oldest  institution  of  its  kind  in 
Boston.  The  care  given  to  these  children  by  the  Sisters  of  Charity 
is  unsurpassed;  therefore  the  conditions  existing  here  may  be  assumed 
to  be  as  nearly  ideal  as  possible  in  any  institution  of  its  kind  in  the 
country.  In  fact  a  comparative  study  of  the  records  of  institutions 
for  the  last  ten  years  has  shown  that  the  ratio  of  infectious  diseases 
here  is  extremely  low. 

The  mouth  conditions  existing  among  the  children  when  work 
was  begun,  Nov.  10,  1910,  would  startle  even  the  most  optimistic 
stomatologist.  Of  the  three  hundred  children  there  was  not  one  who 
ever  had  dental  care,  and  there  was  not  one  child  who  did  not  need 
dental  treatment.  This  condition  exists  in  all  institutions  in  this 
country  where  systematic  dental  work  is  not  done. 

The  following  is  a  summary  of  the  work  accomplished  in  the  last 
thirty-six  months: 

Nov.,  1910,      May,  1912, 

to  to 

May,  1912.      Nov.,  1913. 

Total  number  of  different  patients  examined 349  303 

Total  number  of  cleanings 272  350 

Total  number  of  cement  fillings 25  45 

Total  number  of  amalgam  fillings 72  76 

Total  number  of  cement  amalgam  fillings 69  60 

Total  number  of  temporary  fillings 130  180 

Total  number  of  oxphas  cu.  fillings .9  57 

Total  number  of  teeth  extracted  (temporary)        ....  290  102 

Total  number  of  teeth  extracted  (permanent)        ....  131  51 

Total  number  of  abscesses  opened 42  21 

Total  number  of  gums  cut  for  permanent  teeth     ....  19  9 

Total  number  of  plastic  operations 3  0 

Total  number  examined  and  treated 1421  1245 

Total  number  of  fillings  (including  temporary)      ....  315  418 

Total  number  of  teeth  extracted  (including  temporary)  .      .  421  153 

Total  time  spent  (hours) 210  190 

A  study  of  the  above  table  will  give  an  idea  of  the  gigantic  problem 
confronting  dentists  in  the  handling  of  conditions  existing  in  the 
mouths  of  the  public  school  children  of  this  country. 

On  page  466  is  printed  a  table  containing  the  number  of  infectious 
diseases  occurring  at  St.  Vincent's  Orphan  Asylum  in  the  last  seven 
years. 

In  the  year  1905  to  1906  the  Home  was  in  quarantine  for  over  three 
30 


466 


INSTITUTIONAL   DENTISTRY 


months  because  of  an  epidemic  of  scarlet  fever  of  seventy-five  cases. 
From  the  following  data  it  may  be  seen  that  in  the  last  thirty-six  months 
but  seven  cases  of  infectious  diseases  have  occurred  at  the  asylum. 
Of  these,  six  were  measles,  one  of  which  was  contracted  previous  to, 
or  immediately  after,  admittance  to  the  Home.  The  disease  spread 
to  five  permanent  inmates  of  the  Asylum.  The  mouths  of  all  the  pa- 
tients were  carefully  examined  and  found  to  be  in  need  of  dental  treat- 
ment. AVhereas  in  former  years  from  ten  to  fifty  children  were  stricken 
with  measles,  this  year  only  five  of  them  contracted  the  disease.  The 
one  case  of  diphtheria  also  occurred  in  a  new  girl.  Examination  of  the 
mouths  of  these  seven  children  showed  great  need  of  dental  work. 
What  conclusion  must  be  drawn  from  this  elimination  of  infectious 
diseases  at  St.  Vincent's  Asylum  immediately  after  the  beginning  of 
dental  work,  and  the  continuance  of  this  immunity  for  a  period  of 
three  years? 

RECORD   IN   REGARD   TO   INFECTIOUS   DISEASES. 


1907 

1908 

1909, 

Nov.,  1910. 

Apr.,  1911, 

May,  1912, 

May,  1913, 

to 

to 

Nov. 

to 

to 

to 

to 

1908. 

1909. 

1910. 

Apr.,  1911. 

May,  1912. 

May,  1913. 

Nov.,  1913. 

Diphtheria 

6 

2 

1 

0 

0 

0 

1 

Mumps       .... 

8 

3 

10 

4 

0 

0 

0 

Scarlet  fever    . 

17 

8 

12 

8 

0 

0 

0 

Pneumonia 

3 

5 

4 

6 

0 

0 

0 

Measles       .... 

24 

50 

40 

25 

0 

0 

6 

Ton.sillitis  .... 

19 

16 

8 

3 

0 

0 

0 

Whooping-cough  . 

7 

2 

2 

0 

0 

0 

0 

Chicken-pox     . 

15 

17 

10 

6 

0 

0 

0 

Typhoid     .... 

0 

0 

0 

0 

0 

0 

0 

Croup   

4 

0 

0 

0 

0 

0 

0 

Spinal  meningitis 

0 

0 

0 

0 

0 

0 

0 

Scarlatina  .... 

0 

0 

0 

Bright's  (acute)     . 

0 

0 

Hemorrhage 

0 

Tuberculosis  of  the  eye 

1 

Tuberculosis  of  lungs 

1 

103 

103 

87 

52 

2 

0 

7 

The  above  statistics  demonstrate  clearly  that  there  must  be  some 
relation  between  unsanitary  mouths  and  the  infectious  diseases  of 
childhood.  Dentists  need  no  longer  merely  claim  to  be  prophylactic 
agents  in  the  field  of  medicine.  The  field  is  large  and  it  is  hoped  that 
the  presentation  of  the  above  statistics  may  stimulate  others  to  do 
this  work.  I  am  sure  their  deductions  and  results  will  further 
strengthen  the  importance  of  oral  hygiene. 

A  third  demonstration,  and  one  of  unusual  importance,  was  conducted 
at  Marion  School,  in  1910,  by  W.  G.  Ebersole,  M.I).,  D.D.S.,  Chair- 
man of  the  Oral  Hygiene  Committee  of  the  National  Dental  Associa- 
tion. Miss  Cordelia  D.  O'Neill,  principal  of  the  school,  supervised  this 
demonbtration  and  following  is  a  report  of  this  work  by  Miss  O'Neill: 


MOUTH  HYGIENE  467 


MOUTH  HYGIENE.     WHAT  IT  HAS  DONE.     WHAT  IT  CAN  DO. 

By  CORDELIA  L.  O'NEILL. 

Recently  a  prominent  physician  in  an  address  at  the  Royal  Hospital 
of  London  said: 

"Oral  hygiene — the  hygiene  of  the  mouth — there  is  not  a  single 
thing  in  the  whole  range  of  hygiene  more  important  to  the  public 
than  that." 

He  does  not  stand  alone  in  his  contention.  But  unfortunately  the 
static  approval  rather  than  the  dynamic  refutation  of  this  idea  has 
nullified  the  results  obtainable.  School,  as  we  understand  it,  is  the 
training  camp  for  life.  School  hygiene  intelligently  practised  will 
produce  healthy  and  efficient  life.  Hence  the  wisdom  of  utilizing  every 
phase  of  hygiene  during  this  important  period  of  school  training. 

The  purpose  of  this  chapter  is  to  present  a  report  of  an  experiment 
made  to  test  the  value  of  oral  hygiene  to  mental  ability  and  growth. 

No  doubt  it  has  been  observed  that  the  educational  workl  is  more 
conservative  in  making  innovations  to  fit  the  exigencies  of  the  times 
than  any  other  working  force.  Before  the  first  city  in  the  Ignited 
States  adopted  school  medical  inspection,  pioneer  work  had  to  be  done 
by  the  few  to  demonstrate  to  the  public  its  value.  The  same  experi- 
ence came  to  the  second  city  and  so  on  down  the  ranks.  Cleveland 
was  no  exception.  Conclusive  proof  in  one  comminiity  seemed  to  carry 
no  weight  in  the  neighboring  communities. 

In  1905  the  opportunity  presented  itself  of  doing  some  work  in  medi- 
cal inspection  in  the  school  building.  Since  we  had  always  greatly 
respected  the  thought  of  "A  healthy  mind  in  a  healthy  body,"  and 
also  because  we  had  the  executive  authority,  we  seized  the  opportunity 
and  had  the  work  established. 

At  the  end  of  four  years  the  physical,  moral  and  mental  improvement 
due  to  the  eradication  of  disease  and  the  prophylactic  effort  of  clean- 
liness was  most  marked. 

In  June  of  that  year,  1909,  the  Cleveland  Dental  Society  secured 
the  permission  of  the  Board  of  Education  to  make  an  examination  of 
the  pupils  in  four  buildings  of  the  city — Doan  School  in  one  of  the 
beautiful  resident  sections  of  the  East  End;  Lawn  School  in  a  middle 
class,  well-to-do  section  in  the  extreme  West  End ;  Murray  Hill  School 
in  an  Italian  settlement;  and  ]\Iarion  School  in  a  down-town  congestetl, 
cosmopolitan  and  Ghetto  section. 

The  results  of  the  examination  in  the  four  schools  representing  differ- 
ent types  of  children  showed  that  97  per  cent,  of  the  mouths  were 
in  faulty  condition.  Among  the  846  children  examined  in  jMarion 
School,  only  three  were  found  whose  mouths  were  in  perfect  condition. 
Many  had  teeth  covered  with  green  stain;  some  had  two  or  three 
abscesses.  Disease  and  neglect  were  very  evident.  That  revelation 
was  somewhat  startling  considering  what  had  been  done  for  the  chil- 


468  INSTITUTIONAL  DENTISTRY 

dren.  While  it  did  not  shatter  oiir  faith  in  medical  inspection,  it  proved 
rather  conclusively  that,  though  medical  inspection  is  very  good,  yet 
to  get  the  best  results,  mouth  hygiene  cannot  be  ignored. 

"We  were  therefore  quite  ready  to  co5perate  in  experimental  work 
when  our  assistance  was  asked  by  the  Chairman  of  the  Oral  Hygiene 
Committee  of  the  National  Dental  Association. 

The  proposition  made  by  the  dentist  was  that  if  the  pupils  prac- 
tised oral  hygiene,  and  if  their  teeth  were  put  and  kept  in  a  clean 
healthy  condition,  their  mental  ability  would  be  increased  at  least 
15  per  cent. 

\Ye  knew  that  medical  inspection  for  the  four  preceding  years  had 
increased  the  efficiency  of  our  pupils,  but  we  had  no  way  of  knowing 
how  much  improvement  had  been  made.  We  were  not  disposed  to 
encourage  the  Oral  Hygiene  Committee  to  gather  any  laurels  from  our 
medical  inspection  work;  but  we  were  most  willing  to  lend  every  effort 
to  discover  any  means  of  furthering  the  interests  and  improving  the 
opportunities  of  our  pupils. 

We  believe  the  educator  should  cooperate  with  any  and  every  pro- 
fession that  can  give  aid  to  his  work.  We,  as  educators,  should  be  the 
vanguard  in  the  army  of  reform  and  improvement,  not  only  to  the 
pupils  in  the  class-room,  but  to  humanity  at  large.  It  is  not  for  us  to 
use  tallow-candle  methods  in  this  age  of  electric  light;  or  stagecoach 
theories  in  the  day  of  the  aeroplane.  True,  mental  processes  are  the 
same  as  in  the  time  of  Plato  and  Aristotle,  but  present-day  environ- 
ment and  requirements  demand  the  greatest  conservation  of  human 
energy.  If  the  large  manufacturing  plants  feel  the  necessity  of  main- 
taining at  great  expense  experimental  and  chemical  laboratories,  if 
our  government  supports  experimental  stations  to  obtain  the  maximum 
result  from  the  soil  and  farm  products,  is  it  not  reasonable  to  believe 
that  education  can  be  much  benefited  by  laboratory  experiment  and 
investigation?  Therefore  a  justification  exists  for  a  school  teacher 
assuming  the  responsibilities  of  an  experiment  suggested  and  planned 
by  the  committee  of  the  National  Dental  Association. 

We  had  no  interest  in  the  success  of  dentistry;  and  we  undertook 
the  work  while  in  a  critical  frame  of  mind  somewhat  skeptical  of  the 
claims  made,  but  willing  to  bear  the  chagrin  of  lost  time  and  energy 
if  the  experiment  was  a  failure;  or  receive  sharp  criticism  of  results  and 
motives  if  it  were  a  success. 

Thereff)re  we  agreed  to  begin  the  work  that  would  prove  to  us 
whether  oral  or  mouth  hygiene  practised  faithfully  would  increase 
mental  power. 

Our  first  step  was  to  have  all  the  pupils  in  the  building  carefully 
examined  again  by  a  competent  dentist.  His  assistant  recorded  on 
fluj)licate  charts  the  condition  of  the  mouth  and  teeth  of  each  pupil. 
From  the  charts  of  the  i)upils  in  the  4th,  otli,  (jth  and  7th  grades  we 
selected  the  40  charts  showing  the  worst  oral  conditions.  We  selected 
from  those  particular  grades  because  pupils  below  the  4th  grade  could 


MOVTII   IIYCIIENE  469 

not  sufficiently  understand  tlie  requirements  of  the  mental  tests,  nor 
of  themselves  carry  out  the  practical  care  of  the  mouth.  The  pupils 
of  the  8th  grade  would  be  promoted  into  high  school  before  we  had 
finished  our  experiment  and  we  would  have  too  much  difficulty  in 
getting  the  children  together  for  grou])  meetings.  Having  selected 
only  according  to  the  condition  of  the  mouth  and  teeth,  we  found  that 
the  group  of  forty  represented  a  variety  of  types  of  children.  It  was 
typical  of  the  school.  Some  were  bright,  well-meaning;  some  had 
strong  leaning  toward  incorrigibility,  and  the  others  varied  between 
those  two  extremes.  Many  were  behind  grade.  Of  those  who  com- 
pleted the  tests  8  were  up  to  grade;  9  one  year  behind;  5  two  years; 
3  three  years  and  2  four  years. 

The  services  of  a  psychological  expert  were  secured.  He  planned 
six  sets  of  tests.  They  were  tests  in  memory,  spontaneous  association 
and  differentiation,  perception  and  calculation. 

A  nurse  was  engaged  to  have  supervision  over  the  children,  and 
instruct  them  in  the  necessary  practices. 

The  Chairman  of  the  Oral  Hygiene  Committee  of  the  National 
Dental  Association  had  made  all  plans  and  was  present  when  each  and 
every  test  was  made. 

The  assistant  principal  of  our  building,  a  special  German  teacher,  and 
one  room  teacher  assisted  at  the  test  meetings.  With  this  corps  of 
workers  our  first  meeting  was  held  May,  1910. 

The  children  were  told  the  purposes  of  the  experiment.  They  were 
asked  to  assist  us  in  making  it;  and  were  informed  what  would  be 
expected  of  them  if  they  decided  to  cooperate: 

1.  There  were  expected  to  attend  each  and  every  meeting  called. 

2.  They  were  to  brush  their  teeth  three  times  a  day  during  the  entire 
time  of  the  experiment. 

3.  They  were  to  masticate  their  food  thoroughly  and  were  not  to 
interfere  with  its  proper  insalivation  by  combining  solid  food  with 
liquids  during  mastication. 

4.  They  were  to  keep  the  passages  of  the  oral  cavity  clear  by  correct 
inhalation. 

Each  child  was  to  be  given  free  of  charge  a  tooth-brush,  tooth-pow- 
der, drinking  glass  and  any  dental  work  necessary  to  put  his  teeth  in 
good  condition.  Because  of  the  very  bad  state  of  the  mouths  this 
professional  work  in  most  cases  took  considerable  time. 

Since  we  were  dealing  with  children  it  was  necessary  to  make  our 
appeal  fit  the  comprehension  of  our  subjects.  Pupils  from  the  fourth 
to  the  seventh  grade  could  hardly  be  expected  to  appreciate  the  value 
of  dental  prophylaxis  and  undergo  much  extra  inconvenience  to  prove 
its  worth  to  the  doubting  public.  For  that  reason  a  reward  of  a  five- 
dollar  gold  piece  was  promised  to  each  child  at  Christmas  if  he  faith- 
fully did  his  work.  This  reward  was  feared  by  some  to  be  the  main 
incentive.  But  inasmuch  as  the  children  were  just  as  faithful  and 
responsive  for  the  remaining  seven  months  after  the  gold  pieces  were 


470  INSTITUTIONAL  DENTISTRY 

awarded  as  they  were  before,  we  looked  upon  the  award  as  somewhat 
similar  to  the  helpful  little  tug  guiding  the  ship  out  of  the  harbor  into 
the  open  sea  where  it  is  able  to  direct  its  own  course.  The  thought 
of  a  tangible  reward  started  the  children  in  their  practice.  When  they 
began  to  feel  the  benefit  of  the  work  they  needed  no  further  incentive. 

When  the  children  understood  what  was  required  of  them  five  of 
the  number  immediately  withdrew.  They  were  iniwilling  to  under- 
take the  work. 

The  remaining  thirty-five  took  the  first  psychological  tests.  These 
were,  as  before  stated,  prepared  by  a  psychological  expert.  Minute 
directions  were  given  as  to  the  time  allotted  to  each  test;  the  manner 
of  conducting  each,  and  the  credits  in  marking.  Each  of  the  tests 
were  given  by  the  writer.  The  psychological  expert  was  present  at 
the  first  and  directed  the  manner  of  procedure.    Each  succeeding  test 


1 

t  ■    ■ 

pi 

t S^i^  #  ■*¥ llSik ^»^k 'i! ■ 

^^■•^  TCff               '  ■^KB''^^HPh>-^3!^           '  ^Hi^^^l 

Fig.  227 

was  conducted  exactly  as  the  first.  The  tests  were  all  taken  at  the  same 
time  of  day;  in  the  same  room;  and  each  child  occupying  the  same  seat 
first  assigned  him.  The  (.'hairman  of  the  Oral  Hygiene  Committee  of 
the  National  Dental  Association  timed  the  exercises  with  a  stop-watch, 
always,  however,  assisted  by  one  other  timekeeper.  The  nurse  with 
the  three  teachers  mentioned  before  assisted  in  the  distribution  and 
collcr-tion  of  manuscripts  and  papers.  The  conditions  and  atmosphere 
surroiinding  the  cliildren  during  each  test  were  as  nearly  uniform  as 
it  was  possible  to  make  them.  The  nurse  marked  all  the  papers  fol- 
lowing minutely  each  direction  laid  down  by  the  psychological  expert, 
thus  assuring  uniformity  of  judgment  in  giving  credits. 

Two  tests  were  given  before  the  children  began  to  take  care  of  their 
teeth;  tw(i  were  given  while  the  teeth  were  being  treated,  and  two  after 
all  work  was  finished. 


MOUTH  HYGIENE  471 

After  the  first  psychological  tests  were  given  the  children  were 
shown  l)y  the  dentist  how  to  brush  their  teeth.  The  nurse  followed 
up  the  work  in  their  homes  and  it  was  some  time  before  several  of 
them  had  mastered  the  process. 

They  were  then  taught  how  to  masticate  their  food  properly.  Puffed 
wheat  and  cream  was  given  them;  the  process  of  mastication  and  insal- 
ivation  explained  by  the  nurse;  they  all  chewed  it  until  the  wheat  was 
reduced  to  the  proper  consistency;  then,  when  permission  was  given, 
they  swallowed  it.  This  was  done  to  give  them  a  correct  idea  of  the 
proper  consistency  of  food  before  it  should  be  swallowed. 

All  the  demonstration  work  was  given  in  the  school  building.  All 
the  dental  work  except  extractions  and  some  work  in  orthodontia 
was  also  done  in  a  dental  room  fitted  up  in  the  building.  The  nurse 
then  visited  in  the  homes  at  irregular  intervals  to  see  that  each  indi- 
vidual member  understood  and  was  properly  carrying  out  directions. 
Every  effort  was  made  to  preserve  a  perfectly  normal  atmosphere  in 
the  class-room  and  in  the  home  of  each  child.  No  special  attention  in 
any  way  was  attracted  to  these  children  in  the  dental  squad.  The 
meetings  were  held  after  all  other  children  had  been  dismissed;  notice 
of  meetings  was  given  individually  and  not  by  public  announcement. 
In  fact,  so  quiet  and  commonplace  had  been  our  work  that  some  teachers 
as  late  as  December  of  that  year  did  not  know  who,  if  any,  of  their 
pupils  were  in  the  dental  class.  The  above-named  precautions  were 
taken  to  reduce  to  a  minimum  any  effect  that  might  be  produced  by 
undue  attention  being  attracted  to  the  children.  Anyone  who  has 
dealt  with  children  knows  that  phenomenal  results  may  be  obtained 
from  certain  types  by  singling  them  out  and  bestowing  on  them  unusual 
attentions.     We  strove  to  avoid  any  such  stimuli. 

Experiments  with  human  beings  are  manifestly  more  difficult  to 
conduct  than  wdth  any  other  forms  of  nature.  So  many  influences 
enter  in  to  disturb  the  findings;  so  difficult  is  it  to  control  conditions. 
An  effort  was  made  to  anticipate  every  possible  interference  with  a 
clear,  just  and  candid  result.  We  could  see  nothing  to  be  gained  by 
forcing  conclusions  and  we  stood  ready  at  every  stage  to  censure  any 
movement  that  would  favor  the  point  sought.  As  we  mentioned  before, 
we  had  absolutely  no  interest  in  or  desire  for  proving  the  correctness  of 
the  theory  advanced  by  the  dentist.  So  much  for  the  preparation  and 
conduct  of  the  work.    Now  for  results. 

During  the  time  of  the  experiment  it  was  found  necessary  to  drop 
eight  from  the  class.  If  the  pupils  failed  to  attend  meetings,  showed 
evidence  of  neglecting  to  brush  their  teeth,  or  in  any  w^ay  violated 
directions,  they  were  dropped.  Only  uniformly  correct  work  could  be 
considered.  Twenty-seven  pupils  fulfilled  every  requirement  for 
fourteen  months  to  the  complete  satisfaction  of  those  conducting  the 
experiment.  Their  continuity  of  effort  was  most  commendable  and 
surprising. 

Demonstrations  of  the  home  practice  of  the  children  were  made 


472 


INSTITUTIONAL  DENTISTRY 


during  September  and  October  in  the, school  building.  Each  child 
showed  the  way  in  which  he  had  been  brushing  his  teeth.  Results 
of  daily  application  were  very  evident.  A  dinner  consisting  of  meat, 
vegetables,  fruit,  breadstuffs,  etc.,  was  served.  The  children  ate 
under  close  observation  and  each  child  showed  that  he  mastered  what 
had  been  taught  him;  that  he  was  forming  correct  habits  of  mastica- 
tion and  insalivation. 

The  psychological  tests  were  given  as  we  said,  two  before,  two  during, 
and  two  after  the  oral  imperfections  were  corrected.  When  the  com- 
parisons were  made  and  the  records  of  the  tests  completed  it  was  found 
that  the  class  average  showed  a  gain  of  99.8  per  cent,  plus,  and  that  no 
individual  gain  was  less  than  twice  the  15  per  cent,  originally  claimed. 
That  is,  those  children,  the  majority  of  them  repeaters,  taken  collec- 
tively, had  almost  doubled  their  mental  power.  Nor  was  that  all. 
There  was  a  very  marked  improvement  in  the  health,  complexion, 


.-A.      «rrHI 

.^A*     -^ 

r^ 

■p^o 

w^'^S^ 

I^M  -,  ^'ii^ 

P^r^ 

■1 

1   * 

*, 

-    '      - 

M  «■ '.-;,;?-- 

mk  k  ar-.'^'WBi  m 

.^^^^;^^    ,    , 

_ 

.■      -       . 

Fig.  228 


appearance  and  conduct  of  the  children.  It  was  a  revelation  to  those 
who  were  dealing  with  them.  The  self-respect  that  was  engendered  in 
each  pupil  by  the  consciousness  of  a  clean  mouth  was  of  great  value  even 
if  the  improvement  could  not  be  calculated  in  the  form  of  percentage. 
Making  every  allowance  for  a  natural  normal  growth,  as  we  knew  these 
children,  we  believe  the  great  improvement  mentally,  phj^sically  and 
morally  was  due  to  the  practice  of  Oral  Hygiene. 

We  will  now  review  the  case  histories. 

Six  children  did  last  year  in  twenty-four  weeks  the  same  work  regu- 
larly done  in  thirty-eight  weeks,  and  were  graduated  for  high  school 
in  February  instead  of  in  June. 

One  child  was  quarantined  on  account  of  scarlet  fever  in  his  home. 
He  helped  nurse  the  younger  children,  and  every  one  of  the  six  chil- 
dren in  the  family  contracted  the  disease  except  himself.  The  attend- 
ing physician  attributed  his  immunity  to  his  healthy  physical  condition. 


MOUTH  iiraiENE  473 

One  child  was  weak  and  nervous,  and  subject  to  frequent  headaches. 
Not  only  has  she  grown  robusc,  but  her  headaches  have  disappeared. 


Fig.  229.— Sol  Katzel. 


Fig.  230.— Frank  Silverstein. 


Fig.  2.31.— Jake  Bernstein. 


Fig.  232.— Joe  Todd.  Fig.  233.— Lillie  Gottfried. 


474  IXSTITUTIOXAL   DENTISTRY 

One  child,  in  ]May,  1910,  was  in  the  sixth  grade.  In  May,  1911, 
one  year  later,  he  was  graduated  from  the  eighth  grade,  having  accom- 
plished two  entire  grades  in  one  year.  He  had  failed  through  indiffer- 
ence the  ^•ear  before. 


Fig.  2.34.— Helen  Wright. 


One  boy,  at  our  district  athletic  meet  that  year  (1911),  won  first 
place  in  the  lightweight  dash  and  first  place  in  standing  broad  jump, 
securing  almost  two-thirds  of  all  the  points  won  b\'  the  school.    The 


Fig.  2.35.— Sam  Katzel. 


preceding  year,  although  competing,  he  did  not  win  one  point;  he  says 
that  his  success  was  due  to  oral  hygiene. 


Fig.  2.36. — Ben  Dimenstein. 


A  certain  young  girl  had,  1  believe,  the  hardest  struggle  in  the  class. 
Her  teeth  were  very  irregular,  the  worst  case  of  malocclusion  the  writer 


MOUTH  HYGIENE 


475 


has  seen.     During?  the  winter  her  mother  met  with  an  accident  and 
was  taken  to  the  hospital  for  an  operation,  leaving  in  the  child's  care 


Fig.  237. — Beckie  Goldstein,  aged  thirteen  years.     Grade  6th.     Average  increase 
in  working  efficiency,  27.02  per  cent.     Marion  School  Class. 

a  baby  two  weeks  old.     This  baby  w^as  the  sixteenth  in  the  family, 
and  she  the  oldest  daughter.    For  two  months  she,  with  the  help  of  a 


Fig.  238. — Rose  Leiberman. 


younger  sister  and  with  the  advice  and  help  of  some  women  in  the 
neighborhood,  cared  for  the  baby,  regulated  the  household,  and  came 


Fig.  239. — Lillie  Semlakowsky. 


to  school  occasionally  one  or  one-half  day  when  she  found  some  neigh- 
bor who  would  take  the  baby  for  a  time.    By  so  doing  she  kept  in  touch 


476 


INSTITUTIONAL  DENTISTRY 


with  the  work  at  school,  and  was  promoted  with  her  class  in  June. 
But  the  most  remarkable  fact  is  that  during  that  time,  though  she  had 


Fig.  240.— LUlie  Cohen. 


not  one  unbroken  night's  rest  on  account  of  her  anxiety  for  the  baby, 
she  retained  her  vigor  and  strength  through  it  all. 


Fig.  241.— Anna  Pankuch. 


Three  girls  now  have  beautiful  sets  of  teeth,  and  have  made  a  most 
marked  improvement  in  complexion.  Their  improvement  may  be 
said  to  be  esthetic. 


Fig.  242. — llaclicl  Somers. 


One  girl  had  severe  kidney  trouble,  and  was  a  fragile,  delicate, 
nervous  child.  In  every  respect  she  has  greatly  improved  and  is 
sturdy  and  well  today. 


MOUTH  HYGIENE 


477 


Another  girl  led  her  class  in  the  last  promotions. 
Seven  girls  in  the  dental  class  have  shown  improvement  in  scholar- 
ship, behavior,  health  and  appearance. 


Fig.  243. — Gussic  Hammerschlag. 


Fig.  244. — Beatrice  Kramer. 


Fig.  245. — Bertha  Semlakowsky. 


Fig.  246. — Sarah  Macklin. 


478  INSTITUTIONAL  DENTISTRY 

A  young  Russian  girl  has  not  had  the  full  quota  of  mental  endow- 
ments.    She  has  been  in  America  about  three   years.     She  has  had 


Fig.  247. — Frieda  Goldman. 


many    difficulties   to    overcome,    but   nevertheless    made   a   gain   of 
444.82  per  cent.,  besides  improving  greatly  physically. 


Fig.  248.— Selma  Perlick. 


A  certain  young  girl  has  been  the  most  timid  child  in  the  class.  Her 
fear  of  the  dentist  was  such  that  at  first  the  teacher  remained  with 
her,  and  held  her  hands  while  the  dentist  worked.  She  responded 
less  readily,  though  she  mafle  a  gain  of  101.83  per  cent. 


Fig.  249. — Helen  Cohen. 


Two  of  the  boys  in  the  dental  class  ha\e  l)een  good,  faithful,  stea,dy 
workers  and  have  made  gain?,,  besides  brightening  up  and  showing 
physical  growth. 


MOUTH   HYGIENE 


479 


The  banner  pupil  was  a  l)()y.     He  had  ideas  pecuharly  his  own  as 
to  what  a  boy's  duties  and  privileges  were.    These  ideas  were  so  much 


Fig.  250. — Hannah  Cohen. 


Fig.  251.— Ida  Goldman. 


Fig.  252.— Abe  Meyer. 


Fig.  253. — Harry  Freeman. 

at  variance  with  the  conventional  standards  that  difficulties  arose, 
which  were  seemingly  insurmountable  at  times.    Since  working  with 


480  INSTITUTIONAL  DENTISTRY 

the  class  he  has  been  manly,  tractable,  and  does  not  apparently  have 
the  temptations  that  repeatedly  assailed  him  and  were  almost  the 
means  of  his  downfall.  The  result  obtained  for  him  alone  was  worth 
all  om"  effort. 

"We  believe  that  those  children  have  been  greatly  improved  by  what 
has  been  done  for  them  through  living  up  to  the  rules  of  mouth  hygiene. 
The  smallest  part  of  the  good  that  came  to  them,  it  seemed  to  us,  was 
the  mental  improvement  which  was  being  tested.  Important  as  that 
was  and  signijficant  as  it  may  be,  the  gains  of  which  we  took  no  cog- 
nizance, and  could  not  estimate  equally,  benefited  the  children  both 
for  themselves  and  for  the  community  in  which  they  are  soon  to  be 
a  factor. 

Before  the  close  of  the  tests,  the  teacher  had  each  of  the  twenty- 
seven  children  \\T\te  her  a  letter  telling  what  he  or  she  thought  of  the 
work  which  was  being  done.  Each  and  every  letter,  though  varying 
in  other  respects,  spoke  of  the  benefits  the  work  had  brought  to  them. 
They  expressed  their  gratitude  and  they  have  not  changed  their  atti- 


FiG.  254. — Morris  Krouse. 

tude  to  this  day.  That  was  not  unimportant.  They  have,  so  far  as 
the  writer  has  been  able  to  follow,  kept  up  the  personal  care  of  their 
teeth.  The  self-respect  of  a  clean  mouth  is  valuable.  If  we  are  today 
a  race  of  food-bolters  it  may  be  worth  something  to  start  the  next 
generation  with  the  knowledge  of  the  necessity  of  proper  insalivation 
and  mastication  and  help  them  to  form  the  habit  of  putting  that 
knowledge  into  practice.  The  purely  physical  benefits  make  it  worth 
while,  even  without  consideration  of  the  mental.  Though  to  educa- 
tion, in  the  common  acceptation,  mental  power  is  of  highest  concern. 
We  have  met  the  following  criticisms  since  finishing  our  work: 
First,  it  was  claimed,  the  number  of  pupils  was  too  small  to  furnish 
a  basis  for  conclusions.  When  the  I'nited  States  Government  was 
making  its  industrial  investigations  conducted  by  the  Department  of 
Commerce  and  Labor,  10  per  cent,  of  any  particular  class  was  con- 
sidered a  sufficient  number  on  which  to  base  conclusions.  We  had 
selected  the  number  which  the  United  States  Government  considered 
sufficient,  and  that  certainly  was  large  enough  for  the  purpose. 


MOUTH  HYGIENE  481 

Again  we  were  criticized  for  not  taking  weight,  height,  respiration, 
etc.,  before  and  after  the  tests.  .Since  the  physical  growth  of  children 
(hiring  the  adolescent  jjcriod  is  great  (that  was  the  age  of  most  of  those 
children)  we  decided  to  attempt  no  testing  along  those  lines.  We 
confined  our  efforts  to  the  one  phase — growth  in  mental  power.  It 
was  maintained  before  we  began  that  it  would  be  15  per  cent.  Indi- 
vidually it  was  twice  that.  Taken  as  a  whole  it  was  doubled.  But  it 
carried  with  it  a  physical  and  moral  growth. 

We  were  further  criticized  because  a  control  class  was  not  carried; 
that  is,  a  class  who  were  given  the  tests  but  none  of  the  mouth  hygiene 
work.  We  attempted  only  one  thing.  That  was  to  find  out  if  there 
would  be  a  gain.  We  were  not  sure  there  would  be.  Now  both  can 
be  carried  to  test  how  much  gain  is  due  to  mouth  hygiene  alone. 

Dr.  William  Hunter,  Physician  to  the  London  Fever  Hospital, 
in  an  article  on  oral  sepsis  and  again  in  an  address  before  the  faculty 
of  the  McGill  University,  Montreal,  calls  attention  to  the  serious  results 
that  follow  neglect  to  guard  against  diseased  conditions  in  the  mouth. 
After  ten  years  of  special  investigation  he  has  concluded  that  oral 
sepsis  produces  diseases  of  the  tonsils,  phar^Tix,  stomach,  liver  and 
kidneys.  He  cites  several  instances  in  which  the  correction  of  oral 
conditions  has  cured  the  above-named  ailments.  He  has  put  himself 
on  record  as  believing  that  if  all  danger  of  infection  from  oral  sepsis 
could  be  eliminated  from  the  system,  w^e  might  easily  ignore  all  other 
sources  of  sepsis  in  the  body  since,  as  he  says,  "  It  (oral  sepsis)  is  more 
important  as  a  potential  disease  factor  than  any  other  source  of  sepsis 
in  the  body." 

In  every  published  report  of  school  medical  inspection  of  cities  of 
the  United  States,  that  we  have  been  able  to  obtain,  the  diseases  of 
the  mouth  and  teeth  are  found  to  be  more  numerous  than  any  others 
on  record.  Dr.  Hunter  claims  that  the  only  reason  the  results  of 
disease  from  septic  mouths  is  not  more  prevalent  is  because  of  the 
great  resisting  power  possessed  by  the  mucosa  of  the  mouth  and  gums. 
Why  force  our  systems  to  resisting  poison  when  the  source  of  the  poison 
might  be  eliminated? 

Dr.  Charles  Mayo,  of  Rochester,  Minn.,  said,  "It  is  evident  that 
the  next  step  in  medical  progress  in  the  line  of  preventive  medicine 
should  be  made  by  the  dentists.  The  question  is,  "Will  they  do  it?" 
The  schools  cannot  afford  to  wait  to  see  if  they  do  it.  Medical  inspec- 
tion points  out  to  us  that  the  most  universal  physical  defect  is  oral 
disease.  The  leading  physicians  here  and  abroad  warn  us  of  the  serious 
results  of  oral  sepsis.  A  sore  on  the  surface  of  the  body  discharges  its 
poisons  without  additional  harm  to  the  system.  But  the  decaj'ed 
tooth  and  the  diseased  gum  send  their  poisons  directly  into  all  parts 
of  the  human  sj'Stem  that  will  distribute  it  throughout  the  entire  body. 

IMore  disastrous  results  are  prevented  because  nature  prepares  the 
antitoxin  in  the  system  to  counteract  the  poison. 

In  our  experiment  with  the  children  we  found  that  when  we  relieved 
31 


482  INSTITUTIONAL  DENTISTRY 

Nature  of  the  responsibility  of  counteracting  disease  by  cleaning  the 
mouth,  she  turned  her  attention  to  clearing  the  complexion,  invigorating 
the  body,  stimulating  the  mind,  producing  thereby  a  much  better 
quality  of  boys  and  girls.  That  is  the  aim  of  the  school — the  purpose 
of  education.  If  our  twenty-seven  children  were  improved  as  greatly 
in  one  year  by  practising  mouth  hygiene,  the  same  thing  can  benefit 
others.  Not  a  child  in  that  class  received  medical  attention  of  any 
kind  during  the  entire  time,  except  one  little  girl  whose  adenoids  were 
removed  four  weeks  before  the  last  test — too  late  to  affect  the  results. 
In  this  day  of  crowded  factories  and  keen  competition  our  children 
will  be  better  prepared  to  assume  the  duties  of  citizenship  if  they 
have  formed  the  habits  of  intelligent  personal  cleanliness  and  health. 
To  accomplish  this,  we  would  repeat  what  Dr.  Osier  has  said,  that  in 
the  whole  range  of  hygiene  there  is  nothing  more  important  than  oral 
hygiene. 


CHAPTER  XX. 

DENTAL  HYGIENISTS  IN  PUBLIC  SCHOOLS;    AX 

EDUCATIONAL  AND  PREVENTIVE  FORM 

OF  DENTAL  CLINIC. 

By  ALFRED   C.  FONES,  D.D.S. 

Owing  to  the  interest  that  has  been  aroused  throughout  the  country 
and  the  number  of  inquiries  that  have  been  made  regarding  the  detail 
of  the  estabhshment  and  running  of  the  preventive  dental  cHnic  in 
the  pubhc  schools  of  Bridgeport,  it  would  seem  desirable  to  present 
reasons  for  this  type  of  clinic  in  preference  to  the  reparative  type 
that  has  been  established  in  a  number  of  cities,  and  to  describe,  in 
considerable  detail,  the  operation  of  the  Bridgeport  clinic. 

It  hardly  seems  necessary  to  present  additional  argument  why  the 
dental  profession  must,  in  some  practical  manner,  solve  this  universal 
problem  of  decayed  teeth  and  unsanitary  mouths. 

Few  realize  the  pernicious  condition  of  the  teeth  of  the  great  majority 
of  children  in  the  public  schools  throughout  the  country,  and  those  who 
have  a  realization  of  it  are  at  a  loss  to  find  a  solution  of  the  problem. 
For  the  past  few  years  our  dental  literature  has  teemed  with  articles 
on  the  evil  results  of  unhygienic  mouth  conditions,  and  of  late,  since 
scientific  investigations  have  been  made  of  the  systemic  infections  from 
pyorrhea  alveolaris  and  blind  abscesses,  the  necessity  of  adopting  some 
practical  plan  to  prevent  at  least  a  portion  of  this  great  evil  must  be 
plain  to  all.  It  might  even  be  called  the  greatest  evil,  for  there  is  noth- 
ing in  modern  civilization  that  is  the  cause,  either  directly  or  indirectly, 
of  so  much  sickness  as  decayed  teeth  and  unclean  mouths.  Such 
mouths  are  ideal  breeding-grounds  for  germ  life,  and  children  with 
such  mouths  are  far  more  susceptible  to  infectious  diseases  than  those 
whose  teeth  are  sound  and  whose  mouths  are  kept  clean  and  free  from 
food  debris.  The  most  conspicuous  defect  of  the  child  is  the  unsanitary 
condition  of  its  mouth. 

Before  explaining  our  method  of  handling  this  preventive  clinic, 
let  us  consider  the  proposition  as  a  whole  in  order  to  better  judge 
whether  we  are  attacking  the  problem  from  a  logical  view-point  or  not. 
In  almost  all  of  our  cities  the  children  throughout  the  public  schools 
will  average  close  to  six  cavities  per  child.  By  multiplying  the  number 
of  children  in  the  public  schools  of  a  city  by  six,  a  fairly  close  estimate 
may  be  made  of  the  number  of  cavities  that  should  be  filled.  In  a  city 
of  twenty  thousand  school  children  it  would  take  a  corps  of  twenty- 
five  dentists  nearly  two  years  to  properly  restore  these  mouths  to  a 


484  DENTAL  HYGIENISTS  IN  PUBLIC  SCHOOLS 

sound  aiul  healthful  condition.  Such  an  expensive  charity  is  clearly 
out  of  the  question  for  several  reasons:  (1)  Our  city  officials  do  not, 
as  yet,  sufficiently  appreciate  the  immense  importance  of  the  teeth  to 
good  health  to  be  willing  to  appropriate  an  adequate  sum  of  money  for 
the  work.  (2)  Unless  it  were  followed  by  a  definite  system  of  pro- 
phylaxis in  the  schools,  such  work  would  be  only  palliative,  and  in 
but  a  few  years  an  equal  number  of  cavities  would  again  have  accumu- 
lated. (3)  Until  a  greater  interest  in  the  care  of  their  mouths  is 
aroused  among  the  children  and  their  parents,  the  making  of  such 
operative  work  compulsory  would  cause  much  trouble.  (4)  It  is  a 
hopeless  and  endless  task,  for  it  does  not  stop  the  flood  at  the  source, 
but  merely  repairs  the  damages  after  they  occur.  Let  the  facts  be 
accepted  then  as  found  and  let  it  be  admitted  that  the  task  of  filling 
all  the  decayed  teeth  for  the  children  is  an  impossible  one.  But  by 
confining  all  efforts  at  first  to  the  children  of  the  first  grade  where  the 
permanent  teeth  are  just  erupting,  giving  these  mouths  thorough 
prophylactic  treatments  four  or  five  times  during  the  school  year,  and 
educating  the  children,  by  tooth-brush  drills  and  class-room  talks,  as 
to  how  to  keep  their  teeth  free  from  food,  the  decay  of  permanent 
teeth  can,  to  a  great  degree,  be  prevented  and  the  children  saved  from 
the  necessity  of  extensive  dental  operations. 

This  is  the  system  by  which  the  Bridgeport  clinic  is  operated. 

As  the  children  advance  to  the  second  grades  the  corps  of  dental 
hygienists,  trained  for  the  work,  take  care  of  them  in  their  second  year 
of  school  life.  Again  in  the  third  year  and  so  on  up  to  and  including 
the  fifth  year.  Additional  women  are  added  to  the  corps  when  needed 
so  that  the  child  will  have  his  teeth  kept  clean  and  polished  during  the 
first  five  years  of  his  school  life.  From  the  beginning  of  the  system  there 
is  always  an  army  of  children  with  clean  mouths  in  the  first  grade, 
advancing  the  next  year  to  the  second  grade.  Again  this  clean- 
mouthed  army  advances  into  the  third  grade  and  so  on  up  to  the 
fifth,  pushing  before  it  those  who  have  innumerable  decayed  teeth. 
In  five  years'  time  practically  all  of  the  children  in  the  first  five  grades 
will  have  clean  mouths  and  reasonably  sound  permanent  teeth,  and 
if  this  education  and  training  means  all  that  it  should,  in  eight  years 
the  children  in  all  the  grades  will  have  healthy  mouths,  with  the  new- 
comers entering  into  a  definitely  formed  system. 

Such  a  clinic  becomes  a  part  of  the  school  life  and  is  not  to  be  con- 
sidered in  any  sense  as  a  charity.  All  children  in  the  schools,  whether 
of  rich  or  poor  parents,  undergo  an  examination  of  their  mouths  and 
a  jjrophylactic  treatment  of  the  surfaces  of  their  teeth,  accepting  it  as 
much  a  part  of  school  life  as  their  lessons  in  arithmetic  or  geography. 
A  preventive  clinic  of  this  type  is  based  on  a  system  which  harmon- 
izes with  our  American  institutions  that  have  for  their  motto,  "We 
help  those  who  help  themselves."  In  this  way  the  municipality  accepts 
one-half  of  the  responsibility  in  aiding  and  educating  the  children  to 
care  for  their  mouths  and  to  prevent  dental  decay.    The  other  half, 


ORGANIZATION  485 

the  home  care  of  the  mouth  and  the  eating  of  proper  foods,  must  be 
assumed  by  the  child  and  his  parents. 

This  work  in  the  schools  is  essentially  woman's  work,  and  is  the  great 
jSeld  for  the  dental  hygienist,  to  whom  it  opens  up  paths  of  usefulness, 
activity  and  insi)iration  hitherto  undreamed  of,  allying  her  with  the 
workers  of  the  world  who  are  helping  humanity  in  masses. 

LAW. 

Section  12,  Connecticut  Dental  Law,  pertaining  to  Dental  Ily- 
gienists. 

"Any  registered  or  licensed  dentist  may  employ  women  assistants 
who  shall  be  known  as  dental  hygienists.  Such  dental  hygienists  may 
remove  lime  deposits,  accretions  and  stains  from  the  exposed  surfaces 
of  the  teeth  and  directly  beneath  the  free  margins  of  the  gums,  but  shall 
not  perform  any  other  operation  on  the  teeth  or  mouth  or  on  any  dis- 
eased tissues  of  the  mouth.  They  may  operate  in  the  office  of  any 
registered  or  licensed  dentist  or  in  any  public  or  private  institution 
under  the  general  supervision  of  a  registered  or  licensed  dentist.  The 
dental  commission  may  revoke  the  license  of  any  registered  or  licensed 
dentist  who  shall  permit  any  dental  hygienist,  operating  under  his 
supervision  to  perform  any  operation  other  than  that  permitted  under 
the  provisions  of  this  section."    (Public  Acts  of  1915,  Chapter  316.) 

(When  schools  are  organized  for  the  education  of  dental  hygienists 
within  reasonable  distance  of  the  women  of  Connecticut,  an  efi'ort  will 
be  made  to  have  an  educational  and  examination  clause  added  to  this 
section.) 

LIMIT  OF  SERVICE. 

From  the  preceding  section  of  the  dental  law  it  will  be  noted  that 
the  hygienist  is  not  permitted  to  fill  teeth  or  to  do  any  operations  in 
dentistry,  aside  from  that  clearly  specified  in  the  law.  Her  field  of 
service  is  confined  to  the  surfaces  of  the  teeth  and  the  education  of 
individuals  regarding  the  home  care  of  their  mouths  and  the  general 
subjects  of  hygiene. 

ORGANIZATION. 

The  Bridgeport  Board  of  Health  appointed  a  sub-committee,  known 
as  the  dental  committee,  to  conduct  the  work  in  the  public  schools. 
This  committee  comprised  four  dentists  and  one  member  of  the  Board 
of  Health,  who  is  a  physician.  It  had  complete  charge  of  the  installa- 
tion of  the  dental  clinic  in  the  public  schools,  selected  the  supervisors 
and  saw  to  the  selection  and  education  of  the  dental  hygienists.  All 
their  recommendations  of  appointment,  however,  had  to  be  passed  on 
by  the  Board  of  Health;  also  all  expenditures  of  money,  in  order  to  have 
the  work  legal  and  in  harmony  with  the  city  charter.  Monthly  reports 
are  submitted  to  the  Board  of  Health  by  the  chairman  of  the  dental 


486  DENTAL  HYGIENISTS  IN  PUBLIC  SCHOOLS 


Fig.  255. — Dental  corps  in  the  public  schools  of  Bridgeport,  Conn.,  session  of  1915-16, 
comprised  of  one  woman  dentist,  two  supervisors,  and  fourteen  dental  hj'gienists. 


Fig.  256 


Fig.  257 


Figs.  25G  and  257. — Cabinet.  This  form  of  ca))inet  has  been  found  practical  for  use 
in  the  schools.  Height,  .36  inches;  depth,  11 2  inches;  widtli,  18  inches;  upper  drawers, 
4 2  inches  deep;  lower  drawer,  6  J  inches  deep. 


SUPERVISORS 


487 


committee  showing  all  work  done  during  the  month  by  the  super- 
visors anfl  hygienists. 

Fig.  258 


Fig.  259 


( 

Figs.  258  and  259. — Supply  chest.  One  for  each  pair  of  hygienists,  containing  sup- 
plies necessary  for  three  months.  Inside  dimensions:  length,  24  inches;  width,  20 
inches;  depth,  15  inches.  Divided  into  two  compartments — larger  compartment 
20  X  17  X  15  inches,  smaller  compartment  20  x  6^  x  15  inches. 


SUPERVISORS. 

Two  women  supervisors  were  selected  from  a  class  of  trained  hygien- 
ists, one  having  been  a  visiting  principal  in  the  public  schools,  and  the 
other  a  registe^pd  nurse.    The  duties  of  the  supervisors  are  to  super- 


488 


DENTAL  HYGIENISTS  IN  PUBLIC  SCHOOLS 


vise  the  work  of  the  hygienists  in  the  schools,  each  having  an  equal 
number  of  hygienists  in  her  corps  and  under  her  charge.  They  give 
class-room  talks,  tooth-brush  drills,  attend  to  the  distribution  of  liter- 
ature to  the  children,  and  of  all  supplies  to  the  hygienists,  and  make 


Fig.  2G0- — Supervisors  and  dental  hygienists  at  work  in  school  corridors. 

arrangments  for  the  location  of  the  latter  in  the  schools  and  for  the 
moving  of  their  equipments.  The  chairman  of  the  dental  committee 
keeps  in  touch  with  the  supervisors,  almost  daily,  by  visiting  the 
schools  and  he  aids  them  in  solving  any  problems  that  arise. 


IIYGIENISTS 


489 


HYGBENISTS. 

The  hygienists  usually  work  in  pairs,  two  being  assigned  to  a  school, 
unless  the  school  is  exceptionally  large.  Each  hygienist  is  provided 
with  an  equipment  which  becomes  hers  to  work  with  and  which  she  is 


Fig.  261. — Supervisors  and  dental  hygienists  at  work  in  school  corridors. 


supposed  to  keep  in  good  condition.  She  is  first  taught  how  to 
assemble  the  portable  chair  and  then  to  dissemble  and  pack  it  in  its 
box.  Each  hygienist  is  required  to  own  one  complete  set  of  instrum- 
ents, polishers,  water  syringes,  etc.,  the  duplicate  set  being  furnished 


490  DENTAL  HYGIENISTS  IN  PUBLIC  SCHOOLS 

by  the  Board  of  Health.    This  is  done  in  order  to  insure  good  care 
of  the  instruments. 

Hygienists'  Equipment.  The  following  list  comprises  the  full  equip- 
ment of  each  hygienist  and  includes  the  list  and  cost  of  supplies  for 
forty  weeks: 

S.  S.  White  foot  engine $25.00 

Cabinet  with  drawers  and  shelves 8.00 

Stool 10.00 

S.  S.  White  portable  chair 50.00 

Supply  chest 6 .  00 

Oil-cloth  covers  for  chair,  top  of  cabinet,  and  bibs  (7  sets)        .      .  2 .  50 

[  Nos.    5,   6,    13,  14  Smith  set   oral  prophylactic 

Two     sets     of  I       instruments,  J.  W.  Ivory 5.20 

instruments,  -j  Nos.  17,  18  Darby-Perry  excavators,  S.  S.  White  1.40 

long  handles  I  No.  3  S.  S.  White  scaler,  sickle-shaped      .      .      .  1.20 

[  -t-No.  5  S.  S.  White  explorer 50 

Two       sets       of  /  Large  size  \  t  iir   t  r  r\r\ 

,.  ,          i  a       ^^     ■       M-  W.  Ivory 6.00 

porte  polishers  [  Small  size  j 

2  Dun  cheek-distenders — J.  Austin  Dun  Specialty  Co.,  Chicago    .  .50 

2  mouth  mirrors 2.00 

2  tweezers 1.50 

Phenol  sodique  (2  large  bottles) .90 

Glass  for  phenol .25 

■Pumice  (10  pounds) .50 

Cotton  pellets  (3  boxes) .75 

Orange-wood  sticks  (2  doz.  bundles  large  and  2  doz.  bundles  small)  4.80 

Brush  wheels 2 .  00 

Glass  for  water .10 

Waste  holder .25 

Cotton  holder .50 

2  water  syringes 1 .  00 

Knife 75 

Scissors .50 

Floss  (1  dome  and  3  floss) 3.25 

Rubber  cups  (2  doz.) 1.00 

Platenoid  mandrels  for  rubber  cups  (3) .45 

Carbolic  acid 1.00 

Iodine  (24  oz.) 4.80 

Ammonia 1.00 

White  vaseline .50 

Cheese-cloth  for  napkins  (320  yards) 11.00 

Denatured  alcohol  for  sterilization  (12  qts.) 2.40 

Quart  jar  for  alcohol .10 

Sterno-alcohol  water  heater .50 

Solid  alcohol 5.00 

3  brushes  for  instruments .30 

Ivory  soap 1.00 

Paper  towels 5 .  00 

3  bnishes  for  hands  and  na:'.=! .30 

Oil  for  dental  engine .50 

Cuttlefi.sh  strip.s 1.00 

Shears 1.00 

Permanent  record  cards. 

Examination  blanks. 

Total $172.20 

LOCATION  IN  SCHOOLS. 

The  chairs  are  placed  in  the  schools  in  an  unoccupied  room,  if  such 

is  available,  where  tlie  light  is  good  and  there  is  near  access  to  running 


HYGIENISTS 


491 


water.  In  many  schools,  where  there  is  no  such  availaljle  room  corri- 
dors are  used,  if  wide  enough  to  allow  ample  room  for  marching  lines, 
or  basement  rooms,  if  light  is  good  and  there  is  sufficient  heat. 


Fig.  2G2 


Fig.  263 


Figs.  262  and  263. — Dental  hygienists  at  work  on  unused  stair  landings. 

Deep  landings,  or  cloak  rooms  may  also  be  used.    A  place  may  always 
be  found  in  any  school,  for  the  portable  equipment. 


492 


DENTAL  HYGIENISTS  IN   PUBLIC  SCHOOLS 


HOURS  OF  EMPLOYMENT. 

The  dental  corps  arrives  at  the  schools  at  8.45  in  the  mornings, 
allowing  fifteen  minutes  to  prepare  for  the  first  child  patients.  They 
work  until  dismissal  period  of  the  first  and  second  grades  at  11.45, 

Fig.  264 


Fig.  265 


Figs.  204  and  205. — Deep  landings  are  sometimes  utilized,  when  there  is  ample 
room  for  marching  lines,  or  a  cloak-room  is  often  found  to  be  convenient. 


HOURS  OF  EMPLOYMENT 


493 


and  bcgiimiiig  again  at  1.80;  they  work  tlirough  the  school  period  in 
the  afternoons  and  an  hour  afterward,  or  until  4.30  and  also  on  Satur- 


FiG.  266 


Fig.  267 


Figs.  266  and  267. — There  are  times  that  the  corner  of  a  class-room  has  been  used, 
or  a  basement,  if  there  is  suflBcient  light. 

day  mornings  from  9  to  12.  This  period  after  school  hours,  from  3.30 
to  4.30,  and  Saturday  mornings  is  used  for  work  for  children  other 
than  those  of  the  first  grade. 


494 


DENTAL  HYGIENISTS  IN  PUBLIC  SCHOOLS 


EXAMINATION  BLANKS  AND  RECORD  CHARTS. 

Figs.  2GS  and  209  show  the  form  of  record  charts  used. 


o 

■~" 

2 

Ov 

X 

a 

ja 

H 

■oc 

>0 

IT, 

■0 

0^ 

u 
'J 

Ifi 

4 

a 

.0 

M 

_^ 

j 

HI 

a 

.H 

Q 

T3 

13 

H 

(N 

f^ 

a 

0 

73 

0 

a 

_tj 

>• 

a 

.2 

0 

a 
B 

a 

"3 

*•* 
0 

0. 

B 

V 

B 

U 

tb 

Q 

Q 

^ 

a. 

h 

Cu 

U 

c 

G 

fi 

0 

Z 

H 

cu 

9 

u 

ffl 

E 

0 

ja 

H 

0 

_3 
_0 

0 
0 

■f- 

a 

H 

u 

J4 

■0 

■a 

c 

e 

u 

_0 

2 

0 

0 
0 

B 

< 

(fl 

U 

U. 

s 

D 

Z 

a: 

Fig.  208. — Pertiuinent  record  chart. 


EXAMINATION  BLANKS  AND  RECORD  CHARTS 


495 


1 

1 

1        i 

j 

js ! 

•e 

i 

! 

X 

J3 

« 

a! 

a* 

0> 

V 

01 

ot 

0> 

H 

H 

>> 

H 

H 

1 

a 

0 

c 

B 

M 

« 

"a 
e 

01 

S 

B 

o; 

B 
<3 

< 

19 

fa 

(5 

a 

a 

St 

s 

a 
E 

4) 

H 

E 

0. 

i 

0 

u 

0 

a 
E 

Ot 

H 

E 

5 

fa 

b 

a 

X 

V 

M 

4) 

H 

JS 

»i 

! 

31 

.S 

3 

^ 

> 

X 

tfl 

CS 

g 

B 

JS 

o 

V 
V 

a 

O 

o 

<B. 

GO 

H 

O 

'to 

_3 

o 

0 

E 

1 

u 

CO 

1 

0 

4> 

1 

< 

o 

3 

e 
o 

6 

fa 

w 

e 
75 

e 
en 

E 

Fig.  269. — Form  of  daily  examination  slips. 


The  examination  blank  is  of   sufficient  length  to  permit  of  the 
following  being  printed  at  the  bottom  of  it: 

To  THE  Parents: 

This  chart  shows  the  condition  of  the  teeth  and  gums  in  the  mouth  of  your 
child.  We  thought  that  you  might  be  interested  to  see  it.  The  inner  circle  in  the 
picture  shows  the  baby  teeth  and  the  outer  circle  shows  the  permanent  teeth.  Where 
you  see  a  line  drawn  from  a  tooth  it  shows  that  there  is  a  cavity  in  that  tooth  which 
should  be  filled  by  a  dentist.  We  are  trying  to  prevent  your  child's  teeth  from  decay- 
ing by  cleaning  and  polishing  them  every  three  months  and  teaching  the  child  how  to 
properly  use  a  tooth-brush.  You  can  aid  us  very  much  if  you  will  encourage  the  faith- 
ful use  of  a  tooth-brush  and  also  bear  in  mind  that  candies,  cakes,  bread  and  crackers 
if  left  on  the  teeth  will  cause  them  to  decay.  Supervisor  of  Dental  Clinic. 


496  DENTAL  HYGIENISTS  IN  PUBLIC  SCHOOLS 

The  marks  on  the  teeth  show  the  location  of  cavities  on  either  the 
temporary  or  permanent  set.  From  the  examination  charts,  the  find- 
ings are  copied  on  the  record  charts  which  are  kept  throughout  the 
first  five  years  of  the  child's  school  life.  After  a  copy  is  made  from 
the  examination  chart,  it  is  sent  home  by  the  child  to  the  parents. 

USE  OF  DENTAL  ENGINE. 

The  use  of  the  dental  engine  is  permitted  in  polishing,  when  the  child 
has  never  had  his  teeth  cleaned  before  and  the  stains  are  difficult  to 
remove.  In  such  cases  the  hygienists  are  permitted  to  use  Churchill's 
compound  tincture  of  iodin,  and  the  rubber  cups  with  pumice  in  the 
dental  engine,  previous  to  going  over  the  teeth  with  the  hand  polishers. 

STERILIZATION. 

Duplicate  sets  of  all  instruments  used  in  or  around  the  mouth  during 
the  prophylactic  treatments  are  required  in  order  to  follow  a  proper 
system  of  sterilization.  After  a  prophylactic  treatment  all  instriunents, 
polishers,  cheek-distenders,  water  syringes,  etc.,  are  taken  to  the  wash 
bowl  and  scrubbed  vigorously  with  soap  and  a  stiff  nail-brush  under  a 
faucet  of  running  water.  The  instruments  are  dried  on  clean  cheese- 
cloth and  placed  in  a  wide-mouthed  quart  jar  filled  with  denatured 
alchohol  and  allowed  to  soak  during  the  next  operation  which  is  carried 
on  by  means  of  a  complete  set  of  instruments  which  has  just  been  ster- 
ilized in  a  similar  manner.  The  girl's  hands  are  scrubbed  with  soap 
and  nail-brush  under  running  water,  after  each  prophylactic  treatment. 
The  backs  and  head  rests  of  the  portable  chairs  are  covered  with  slips 
of  white  oil-cloth  and  are  washed  off  with  ammonia  water  after  each 
child  patient.  The  tops  of  the  cabinets  are  also  covered  with  oil-cloth, 
and  over  this  is  placed  a  fresh  paper  napkin  preceding  each  operation, 
so  that  no  infection  may  be  carried  from  one  child  to  the  next  from 
laying  down  instruments  or  polishers.  Water  for  rinsing  the  teeth 
while  operating  is  heated  in  small  aluminum  pans,  on  alcohol  stoves, 
using  solid  alcohol  or  "canned  heat"  for  fuel,  to  insure  freedom  from 
danger  of  fire  or  explosion. 

The  system  of  care,  handling,  and  sterilization  of  instruments  has 
been  approved  by  an  expert  in  bacteriology,  and  work,  under  what 
have  been,  at  times,  trying  circumstances,  has  left  no  doubt  as  to 
the  efficiency  of  such  a   system. 

TOOTH-BRUSHES. 

One  r)f  the  problems  is  the  securing  of  a  good  grade  of  tooth-brushes, 
children's  and  youths'  sizes,  that  may  be  sold  for  five  cents,  and  a  larger 
or  adult  size  for  ten  cents.  Up  to  the  present  time  factory  seconds 
have  been  used,  but  the  market  will  soon  warrant  a  new  brush  for 


TOOTH-BliUSlf   DRILLS  AM)  CLASS-ROOM   TALKS         497 

cliildren,  that  can  be  sold  at  this  price.  Care  must  be  taken  in  a  school 
work  of  this  character,  to  see  that  our  public  institutions  do  not  become 
a  field  for  the  advertising  of  toilet  articles,  such  as  mouth  washes  or 
tooth-jiaste  or  powder.  It  would  seem  much  better  not  to  supply  the 
children  with  samples  of  dentifrices,  etc.,  but  rather  to  give  them  a 
formula  which  they  can  have  made  up  for  a  nominal  price  or  to  advise 
them  how  to  detect  abrasives  that  appear  in  some  of  the  proprietary 
articles. 

TOOTH-BRUSH  DRILLS  AND  CLASS-ROOM  TALKS. 

On  the  day  previous  to  the  drill,  a  circular  is  sent  home  to  the  parents 
of  the  children  telling  what  we  wish  to  accomplish,  and  asking  for 
their  cooperation;  they  are  requested  to  give  their  children  five  cents 
to  pay  for  a  new  tooth-brush.  At  the  time  appointed  for  the  drill  the 
supervisor  and  her  two  assistants  enter  the  school-room  wdth  the  tooth- 
brushes, which  have  been  sterilized,  and  a  tray  from  the  sterilizer, 
the  supervisor  standing  in  the  front  of  the  room  and  the  assistants  to 
the  side  or  rear.  The  supervisor  then  inquires,  "How  many  remem- 
bered to  bring  five  cents  for  a  nice  new  tooth-brussh?  Those  who  did, 
stand."  The  brushes  are  given  to  them,  and  they  sit  down.  "Those 
who  did  not  bring  five  cents  and  have  no  tooth-brush  of  their  own, 
stand."  Tooth-brushes  are  given  to  these  with  the  understanding  that 
they  will  be  trusted  to  bring  it  later  to  their  teacher  for  us.  In  many 
rooms  the  entire  amount  is  collected;  in  some  there  are  a  few  who  fail 
to  bring  the  nickel.  But  no  penalty  or  reproach  is  meted  out  to  them 
if  they  fail  to  do  so,  for  the  teacher  knows  that  it  is  impossible  for  them 
to  bring  it,  so  the  Board  of  Health  must  bear  that  expense.  The  brush 
question  being  settled  the  next  step  is  the  inspection  of  their  hands  to 
see  if  they  are  in  a  fit  condition  to  handle  the  brushes.  If  not,  they  are 
sent  out  to  w^ash  them.  Then  comes  a  five-minute  talk  on  the  impor- 
tance of  the  tooth-brush  being  used  by  its  o^vner  only,  and  on  the  reasons 
why  no  one  else  must  use  it,  and  why  we  need  to  clean  our  teeth;  also 
on  the  times  when  we  should  clean  our  teeth,  viz:  "before  breakfast, 
after  breakfast,  after  dinner,  before  we  go  to  bed."  After  this,  accord- 
ing to  a  regular  form,  the  drill  proper  is  given,  seated,  with  the  assis- 
tants passing  up  and  down  the  aisles  helping  the  children  to  hold  their 
brushes  correctly,  and  to  make  the  right  movements.  We  have  four 
positions  for  holding  the  brush  and  two  movements  in  each  drill. 
At  the  close  of  this  part  comes  another  five-minute  talk  on  the  care 
of  the  brush,  emphasis  being  laid  on  the  great  necessity  of  keeping 
it  clean,  by  a  thorough  washing  in  running  water  before  and  after 
using,  on  rinsing  it  constantly  while  brushing,  and  on  having  a  clean 
place  to  hang  it  up  when  through  brushing.  The  pupils  are  also  asked 
to  repeat  a  number  of  times  when  it  should  be  used  each  day.  Then 
the  drill  is  repeated,  the  children  standing  up.  It  must  be  realized 
that  these  drills  are  intended  to  teach  the  children  the  correct  form  of 
32 


49S 


DEXTAL  HYGI EXISTS  IX  PUBLIC  SCHOOLS 


brushing,  and  are  not  meant  for  the  actual  cleaning  of  the  teeth,  which 
crannot  be  properly  done  in  the  class-room  without  running  water  and 
dentrifrice.  This  would  afford  opportunity  for  making  a  muss,  which 
makes  it  impractical  for  class-room  work.  Also,  we  beHeve  it  to  be 
iiimecessar>'. 


Fig.  270 


Fig.  271 


TOOTH-BRUSH   DRILLS  AND  CLASS-ROOM   TALKS         499 


Fig.  272 


Figs.  270,  271,  and  272. — Supervisor.?  and  assistants  giving  tooth-brush  drills  in 

the  schools. 

At  the  close  of  this  drill  the  children  sit  down,  the  brushes  are  taken 
up  and  placed  in  the  slots  of  the  copper  tray,  washed  separately  under 
running  water  and  placed  in  the  sterilizer  to  remain  until  the  next 
day.    The  copper  trays  of  the  sterilizers  are  punched  with  holes  large 


Fig.  273. — A  cheap,  but  practical  and  effective  sterilizer. 


enough  to  permit  of  suspending  the  brushes  in,  and  representing  the 
form  of  the  class-room,  seats  and  aisles,  the  head  of  each  row  of  seats 
being  numbered. 


500  DENTAL  HYGIENISTS  IN  PUBLIC  SCHOOLS 

Formaldehyde  gas  is  used  as  the  steriHzing  agent.  The  next  day 
another  drill  is  given,  the  brushes  remaining  in  the  sterilizer  during 
the  inter^'ening  night,  after  which  the  brushes  are  wrapped  in  waxed 
paper  and  given  to  the  children  to  be  carried  home. 

The  teachers  were  asked  to  inquire  as  to  who  had  brushed  their  teeth, 
the  aim  being  to  remind  them  of  this  duty  and  to  assist  them  in  form- 
ing the  habit  of  daily  brushing.  We  have  been  much  pleased  on  return 
visits  to  find  a  goodly  number  of  the  children's  mouths  showing  marked 
evidence  of  their  having  brushed  their  teeth  regularly  in  the  meantime. 

On  request  for  the  brushes  to  be  brought  back  for  a  drill,  fully  95 
per  cent,  ha^'e  been  brought  back,  and  at  least  95  per  cent,  of  these 
were  in  fit  condition  to  be  used.  The  dirty  ones  are  thrown  away  and 
new  ones  given  in  their  places. 


Fig.  274. — Brush  wrapped  in  waxed  paper,  ready  to  be  carried  home. 

TEACHERS'  COOPERATION. 

^Yithout  imposing  too  much  extra  work  upon  the  teachers,  they  may 
be  asked  to  cooperate  by  having  all  children  who  have  brushed  their 
teeth  stand  and  be  counted,  morning  and  afternoon,  and  the  number 
marked  on  the  blackboard.  In  turn  those  who  have  not  brushed  their 
teeth  are  counted  and  this  number  recorded  also.  Monitors  keep 
these  daily  records  in  the  various  rooms  and  at  the  end  of  the  month, 
the  room  having  the  best  record  is  entitled  to  hold  the  honor  banner, 
which  reads :  "Honor  Class  for  Clean  ]\Iouths"  for  the  succeeding  month, 
or  until  the  next  record  is  taken.  Those  teachers  who  are  especially 
interested  in  this  work  will  often  talk  to  their  classes  concerning  the 
importance  of  sound  teeth  and  clean  mouths,  and  in  this  way  aid  in 
arousing  the  interest  of  the  children  and  educating  them  upon  the 
subject  between  the  visits  of  the  dental  supervisors  and  hygienists. 

PARENTS'  COOPERATION. 

The  parents'  cooperation  is  secured  principally  by  means  of  liter- 
ature that  is  sent  home  to  them  l)y  the  children.  The  literature  should 
be  generously  illustrated,  as  pictures  attract  the  children  and  interest 
the  x^arents  more  quickly.  It  is  wise,  in  the  beginning  of  this  work,  to 
first  ex])lain  to  the  childrcji  in  the  higher  grades  what  is  intended  to 
be  done,  as  they  can  better  understand  it  and  will  s|)read  it  more  cor- 
rectly throughout  the  neighborhood.    As  soon  as  the  parents  under- 


THE  SCHOOL  DENTIST  501 

stand  that  the  work  is  not  a  charity,  that  there  is  no  filling  and  no 
pain  attached  to  it,  thorough  cooperation  from  the  homes  is  soon 
obtained. 

THE  SCHOOL  DENTIST. 

Upon  entering  the  school  in  the  first  grade,  when  the  children  first 
come  into  the  hands  of  the  hygienists,  it  is  frequently  found  that  their 
six-year  molars  are  slightly  decayed,  small  cavities  developing  on  the 
occlusal  as  well  as  on  the  buccal  surfaces.  It  is  extremely  important 
that  these  small  cavities  be  filled  and  the  molar  teeth  saved,  so  a  woman 
dentist  is  employed  to  go  from  school  to  school,  with  portable  outfit 
and  fill  these  small  cavities  in  the  six-year  molars  for  the  children  in 
the  first  and  second  grades.  This  work  we  term  preventive  dentistry, 
as  the  effort  made  is  to  prevent  development  of  large  cavities  in  these 
important  teeth.  General  reparati\e  dentistry  is  not  done  in  the 
schools  in  liridgeport.  In  order  to  gain  the  consent  of  the  parents  for 
the  filling  of  these. teeth  the  card  printed  below  in  the  form  of  a  folder 
is  sent  home  for  the  signature  of  one  of  the  parents. 

To  THE   Parents  of 

Your  child  needs  dental  attention.  This  is  the  time  to  have  the  small  cavities 
filled  to  prevent  future  loss  of  the  teeth.  If  you  have  a  regular  dentist  will  you  please 
take  your  child  to  have  these  cavities  filled  while  most  of  them  are  small.  If  you  have 
no  regular  dentist  and  wish  them  taken  care  of  in  school,  free  of  charge,  by  the  school 
dentist,  please  sign  the  attached  card  and  return  it  to  the  teacher. 

A.  C.  FoNES,  D.D.S., 
Chairman  of  Dental  Committee. 

ELIZABETH  BEATTY,  D.D.S.: 

You  are  hereby  authorized  to  do  any  dental  work  for  my  child  that  you  maj' 
deem  necessary,  said  work  to  be  without  any  cost  to  me. 

Signed 

Parent  or  Guardian. 

There  is  no  difficulty  in  securing  plenty  of  volunteers  and  signed 
cards  for  this  work.  We  believe  that  operative  work  of  this  nature 
can  best  be  done  in  the  schools  where  the  children  are  so  easily  acces- 
sible. INIuch  difficulty  would  be  encountered  if  it  were  necessary  to 
take  them  out  of  the  schools  to  a  central  clinic. 

In  a  w^ell-organized  school  dental  cHnic  provision  must  be  made  for 
the  relief  of  pain,  from  toothache,  for  any  children  in  the  schools  whose 
parents  are  too  poor  to  pay  for  such  dental  service.  Cards  are  printed 
and  after  being  specially  endorsed,  by  being  countersigned  with  initials 
of  the  chairman  of  the  dental  committee,  ten  are  sent  to  each  of  the 
principals  of  the  various  schools,  who  fill  them  in  as  needed,  and  give 
them  to  the  children  who  are  suffering.  The  child  presents  this  card 
to  a  certain  dentist  in  the  center  of  town,  and  he  relieves  the  pain. 
This  may  necessitate  the  extraction  of  a  tooth  or  its  treatment  and  fill- 
ing. A  record  of  the  operation  and  the  charge  for  it  are  made  on  the 
back  of  the  card,  and  at  the  end  of  the  month  the  cards  with  the  bills 
are  rendered  to  the  chairman  of  the  dental  committee.     These  are 


502 


DENTAL  HYGIENISTS  IN   PUBLIC  SCHOOLS 


checked  up,  and  O.  K.'d  and  the  bill  paid  by  the  Board  of  Health. 
The  relief  clinic,  operated  in  this  manner,  costs  about  $100  a  year. 


Fig.  275. — A  woman  dentist,  with  portable  outfit  at  work  in  the  schools. 


STEREOPTICON  LECTURES  IN  THE  GRADES. 

In  order  to  educate  the  children  in  the  higher  grades  also,  it  was 
found  to  be  advisable  to  use  stereopticon  pictures,  as  they  best  hold 
the  interest  of  the  children  and  have  proven  to  be  the  most  instructive 
method  of  teaching  this  subject.  The  most  practical  lantern  for  this 
purpose  is  a  Bausch  and  Lomb  acetylin  gas  lantern.  A  curtain  of 
white  Holland  linen  eight  feet  deep,  mounted  on  a  roller  eight  feet 
long,  makes  the  screen.  This  roller  is  supported,  by  a  frame  of  black 
enameled  gas  pipes  made  in  sections,  with  screw  joints.  Black  alpaca 
curtains  are  used  to  tack  over  the  windows  of  the  school-rooms  in  order 
to  obscure  the  light.  About  fifty-five  slides  make  u])  the  series  for  the 
first  year's  lectures.  This  includes  talks  on  home  hygiene  and  sanita- 
tion and  its  application  to  and  effect  on  the  body,  the  results  of  neglect- 
ing the  mouth,  ai)i)ealiiig  to  the  girls  through  their  sense  of  beauty,  and 
to  the  bo>'s  through  their  love  of  sports  and  ability  to  do  things,  and 
also  to  ail  the  children  through  stories,  emphasi'/ing  always  that  "A 
clean  tooth  never  decays."  As  this  educational  work  proceeds  the  chil- 
dren will  })(•  taught  the  proper  way  to  use  their  teeth,  how  to  masticate 
their  food,  and  also  what  are  the  ])roper  foods  for  their  bodies.  After 
the  lecture,  when  the  children  are  about  to  leave  for  home,  literature 


STEREOPTICON  LECTURES  IN   THE  GRADES 


503 


is  distributed  to  them  which  they  are  to  take  to  their  homes.  This 
helps  to  impress  tiie  i)riiicipal  points  upon  the  child  and  acquaints  the 
parents  as  well  with  the  subject  we  are  anxious  that  they  should  know 
about  and  understand.  Under  this  form  of  education,  the  younger 
children  should  show  a  much  improved  condition  of  the  temporary 
teeth  in  a  few  years;  while  the  lessons  taught  to  the  older  children  in 
school  are  taken  home,  and  should  result  in  the  parents  giving  more 
attention  to  mouth  hygiene  among  the  little  children  yet  too  young  to 
enter  school. 

During  the  years  1914-15,  with  a  corps  of  eight  hygienists  and  two 
supervisors,  treatments  and  examinations  were  given  to  6768  chil- 
dren. The  total  number  of  prophylactic  treatments  given  was  14,340. 
The  supervisors  gave  tooth-brush  drills  from  October,  1914,  to  June 
20,  1915,  to  12,546  children. 

The  following  table  gives  the  details  of  our  findings  of  the  6768 
children  on  the  first  examination  of  their  mouths : 


State  of  teeth. 

Color  of  gums. 

Fistulas  showing 

Cases  of 

Clean. 

Fair. 

Dirty. 

Dark 
red. 

Light 
red. 

Pink. 

abscessed  teeth.      i         malocclusion. 

401 

2647 

3720 

1573 

4731 

464      1                  691 

6077 

The  use  of  the  tooth-brush. 

Cavities. 

Daily. 

Occasionally. 

Not  used. 

In  temporary  teeth. 

In  permanent  teeth. 

6.53 

2149 

3966 

36,700 

4555 

The  following  table  is  of  more  interest,  as  it  shows  a  comparison  of 
the  mouths  of  the  2780  children  who  have  had  three  or  more  prophy- 
lactic treatments  during  the  year. 

Totals  of  first  and  last  examinations  of  children  receiving  three  or 
more  prophylactic  treatments  during  the  year: 


State  of  teeth. 

Color  of  gums. 

First  examination. 

Last  examination. 

First  examination. 

Last  examination. 

Clean. 

Fair. 

Dirty. 

Clean. 

Fair. 

Dirty. 

Dark 
red. 

Light 
red. 

Pink. 

Dark 
red. 

Light 
red. 

Pink. 

186 

1067 

1527 

873 

1769 

143 

647 

1897 

236 

273 

1981 

526 

Fistulas. 

Malocclusion. 

First  examination. 

Last  examination. 

2494 

317                                       336 

504  DENTAL  HYGIENISTS  IN   PUBLIC  SCHOOLS 

Use  of  TooxH-BRtiSH. 


First  examination. 

Last  examination. 

Daily. 

Occasionally. 

Not  used. 

Daily. 

Occasionally. 

Not  used. 

252 

096 

1S32 

763 

1831 

186 

Cavities. 

Increased  number  of  cavities. 

First  examination. 

Last  examination. 

Temporary 
teeth. 

Permanent 
teeth. 

Temporary 
teeth. 

Permanent 
teeth. 

Temporary 
teeth. 

Permanent 
teeth. 

1623 

499 

15,547                1027 

17,170 

1526 

It  will  be  noted  that  the  increase  of  cavities  in  the  teeth  during  the 
year  has  been  considerably  less  than  one  cavity  per  child. 

The  dental  corps  of  1915-16  of  fourteen  hygienists  are  caring  for 
nearly  double  the  number  of  the  previous  year. 


APPENDIX. 


For  the  benefit  of  any  dental  organizations  that  might  desire  to 
educate  a  class  of  women  as  dental  hygienists  for  private  practice 
or  for  public  service,  as  in  schools,  as,>'lums,  or  hospitals,  the  follow- 
ing suggestions  taken  from  a  course  in  dental  hygiene,  both  theoret- 
ical and  practical,  actually  held,  are  submitted  with  the  hope  that 
they  may  prove  helpful  and  of  value. 

THEORETICAL   COURSE. 

The  theoretical  course  should  extend  over  a  sufficient  period  of  time 
to  give  the  class  a  good  grounding  in  all  essentials  without  crowd- 
ing the  lectures  too  close  together.  In  the  case  in  point  the  lectures 
were  held  in  the  evenings  from  7.30  p.m.  until  9.30  p.m.,  three 
evenings  a  week.  This  arrangement  permitted  women  who  were 
otherwise  occupied  during  the  day  to  take  advantage  of  the  course. 
The  lectures  were  given  according  to  the  following  schedule: 

SCHEDULE. 

Anatomy. 

Physiology. 

Anatomy. 

Physiology. 

Anatomy. 

Physiology. 

Anatomy. 

Physiology. 

Anatomy. 

Physiology. 

Bacteriology  and  Sterilization. 

Special  Anatomy. 

Bacteriology  and  Sterilization. 

Special  Anatomy. 

Bacteriology  and  Sterilization. 

Special  Anatomy. 

Bacteriology  and  Sterilization. 

Special  Anatomy. 


506  APPENDIX 

Inflammation. 

Special  Anatomy. 

Skin  Diseases  and  Syphilis. 

Inflammation. 

Skin  Diseases  and  Syphilis. 

Oral  Secretions. 

The  Teeth  as  a  ]\Iasticating  Machine. 

Dental  Caries. 

The  Chemistry  of  Foods  and  Nutrition. 

The  Teeth  as  a  ^Masticating  IMachine. 

Dental  Caries. 

The  Chemistry  of  Food  and  Nutrition. 

Odontalgia. 

Pyorrhea  Alveolaris. 

Malocclusion. 

Alveolar  Abscess. 

Pyorrhea  Alveolaris. 

Malocclusion. 

Alveolar  Abscess. 

Deposits  and  Accretions  on  the  Teeth. 

Dental  Prophylaxis. 

The  Sanitary  Aspect  of  Dental  Operations. 

Dental  Prophylaxis. 

Posture  and  Fresh  Air. 

I  )ental  Prophylaxis. 

Factors  in  Personal  Hygiene. 

Dental  Prophylaxis. 

The  Teaching  of  Mouth  Hygiene  to  School  Children. 

Dental  Prophylaxis. 

The  Psychology  of  Handling  Children  in  Office  Practice. 

Lengthening  the  Life  of  the  Resistive  Forces  of  the  Body. 

This  order  was  deemed  expedient  to  give  best  continuity  in  build- 
ing up  foundational  knowledge.  Each  lecture  on  physiology  followed 
the  corresponding  one  on  anatomy  and  covered  the  same  ground. 
These  two  subjects  might  even  be  combined  to  advantage  and  given 
together  by  one  lecturer. 

The  class  assembled  at  seven-thirty  and  the  first  half-hour  was 
rlev(jted  to  a  review  of  the  previous  lecture  by  one  of  the  quiz  masters, 
followed  by  the  lecture  of  the  evening. 

In  the  equipment,  student  chairs  with  broad  arms  for  writing  were 
used  for  convenience  in  taking  notes.  A  stereopticon  with  balopticon 
combination  was  also  used,  the  l)alopticon  permitting  of  the  pro- 
jection of  illustrations  from  books,  pictures  or  objects  upon  the 
screen. 

Written  examinations  were  held  as  soon  as  convenient  at  the  com- 
pletion of  the  most  important  subjects. 


THEORETICAL  COURSE 


507 


508 


APPENDIX 


THEORETICAL  COURSE 


509 


510  APPENDIX 

PRACTICAL   COURSE. 

At  the  conclusion  of  the  theoretical  course  of  various  studies,  the 
course  of  practical  training  in  prophylaxis  was  arranged  for  and  taken 

The  class  of  thirty-two  women  was  divided  into  two  classes,  sixteen 
in  each,  one  to  work  two  hours  in  the  afternoons,  Mondays,  Wednes- 
days and  Fridays  from  4  p.m.  until  6  p.m.,  and  the  other  on  evenings  of 
the  same  days  from  7.30  p.m.  mitil  9.30  p.m. 

The  lecture-room  was  cleared  of  its  desk  chairs  and  transformed  into 
a  veritable  clinic-room. 

The  balopticon  and  the  screen  were  left  for  use  in  the  practical 
work,  and  sixteen  modern  dental  chairs,  with  attachments  of  work 
tables  and  cuspidors,  were  installed,  arranged  around  the  room  facing 
the  center,  four  on  each  side  and  four  on  each  end.  Electric  drop 
lights  were  hung  over  each  chair. 

^lanikins,  for  first  practise,  were  purchased  and  attached  to  the 
chairs  in  the  place  of  head  rests  and  hoods  of  rubber  cloth  made  to  fit 
under  the  chins  and  back  of  the  jaws  of  the  manikins  to  catch  the 
water  used  in  s^Tinging  the  teeth.  A  piece  of  rubber  dam  about  eight 
inches  sc^uare,  through  which  a  hole  was  perforated  for  the  rod  attached 
to  the  manikin  to  pass  through,  was  tacked  to  the  wooden  portion  at 
the  back  of  the  head  of  the  manikin.  This  arrangement  inside  of  the 
rubber  hoods  deflected  the  water  into  the  hoods.  Eyelets  on  the  upper 
corners  of  the  bags  and  hooks  on  the  manikins  facilitated  emptying 
the  bags  after  use.  In  the  center  of  the  room  a  large  sink  was  built, 
with  running  water,  both  hot  and  cold,  and  with  zinc  table  large  enough 
to  accommodate  a  tub  for  boiling  water  to  use  for  sterilizing  instru- 
ments when  the  practical  work  upon  children  should  be  reached.  The 
water  was  boiled  and  kept  boiling  by  an  electric  heater.  Sixteen  deep 
metal  cups,  perforated  near  the  bottom  and  fitted  with  wire  handles 
which  allowed  the  cups  to  be  immersed  in  the  boiling  water  and  the 
instruments  inside  to  be  sterilized,  were  hung  over  and  around  the  edge 
of  the  tub.  Rolls  of  absorbent  paper  toweling  for  general  use  were 
attached  to  the  sink,  and  bottles  of  liquid  soap  placed  upon  it.  Upon 
the  sink  also  were  cans  of  powdered  pumice  and  trays  for  alcohol  to 
be  used  for  sterilizing  mirrors  and  handles  f)f  instruments  that  would 
not  stand  the  boiling  water. 

Each  pupil  was  provided,  at  cost,  with  a  japanned  box  fitted  with 
lock  and  key  in  which  to  keep  her  own  instruments,  and  the  following 
list  of  instruments  andutensils  also  furnisherl  her  at  cost: 


PRACTICAL  COURSE  511 


LIST   OF  INSTRUMENTS  AND  UTENSILS. 

Bib-holders  and  paper  bibs. 

]\Iouth  mirror. 

Phenol  sodique  (small  bottle). 

Holder  for  phenol  sodique. 

Darby-Perry  instruments,  Xos.  17  and  18.    (S.  S.  White.) 

Harlan  instruments,  Nos.  3  and  4.    (S.  S.  White.) 

Smith's  set  instruments,  Nos,  5  and  6.    (J.  W.  Ivory.) 

Smith's  set  instruments,  Nos.  13  and  14.    (J.  W.  Ivory.) 

Sickle-shaped  instrument,  No.  3.    (S.  S.  White.) 

Explorer. 

I  )unn  cheek-distender. 

Pumice  dish. 

Waste  receiver. 

Cotton  pellets  and  holder. 

Large  porte  polisher  and  large  orangewood  sticks. 

Small  porte  polisher  and  small  orangewood  sticks. 

Brush  wheels. 

Glass  for  water. 

Water  bulb. 

Tooth-brush. 
Each  pupil  was  required  to  provide  herself  with  two  white  linen 
aprons  (Standard  pattern,  No.  (3993),  for  wear  at  work  and  at  practise, 
and  the  classes  were  ready  to  begin  their  lessons  and  training. 

The  first  lesson  to  both  classes  consisted  in  a  review  of  what  had  been 
given  before  in  the  theoretical  course  of  the  four  motions,  digital, 
wrist,  rigid-arm  and  rotary,  necessary  to  skill  in  handling  both  instru- 
ments and  polishers,  pictures  being  thrown  upon  the  screen  to  illus- 
trate them.  The  ordinary  order  of  work — first  instrumentation  and 
then  polishing — was  reversed  because  the  polishing  would  give  the 
motions  in  more  pronounced  form,  and  so  the  class  was  instructed  to 
place  the  large,  orangewood  sticks  which  had  been  previously  cut  and 
whittled  to  proper  shape  and  size  into  the  large  porte  polisher  and  the 
system  of  polishing  begun. 

The  lights  were  put  out  and  the  picture  illustrating  the  first  division 
of  polishing  was  thrown  upon  the  screen.  This  was  studied  in  regard 
to  teeth  in^'o^ved,  surfaces  to  be  covered,  grasp  of  the  polisher,  fulcrum- 
point  for  the  hand  and  the  motion  used.  After  this  detailed  explana- 
tion the  lights  were  turned  on  and  each  student  applied  these  principles 
to  the  teeth  of  the  manikin,  the  instructor  passing  from  chair  to  chair 
to  see  that  the  work  was  being  done  correctly.  This  procedure  was 
followed  with  each  division,  and  the  entire  system  of  polishing  greatly 
simplified  for  the  pupils  by  the  series  of  photographs  of  the  different 
slides  with  which  they  were  provided  for  their  own  use,  as  well  as  type- 
WTitten  lists  of  the  seventeen  divisions  into  which  the  mouth  is  divided 
for  best  convenience  and  least  loss  of  time  in  changing  positions. 


512  APPENDIX 

The  first  five  lessons  were  devoted  to  polishing  according  to  the 
schedule  appended,  and  then  the  first  lesson  in  instrumentation  was  given. 
The  class-room  was  open  from  10  a.m.  until  10  p.m.  on  the  days  when 
there  were  no  lessons  and  on  lesson  days  from  10  a.m.  until  4  p.m., 
except  that  as  the  instrumentation  lessons  proceeded,  time  must  be 
allowed  for  putting  the  mixture  of  plaster  and  varnish  on  the  teeth 
of  the  manikins  and  letting  it  harden. 

^Yhen  the  practical  examination  in  polishing  was  held,  the  teeth  of 
the  manikins  were  removed  and  each  member  of  the  class  required 
to  blacken  the  set  of  another  member  with  a  broad  carpenter's  pencil, 
using  an  ordinary  pencil  for  making  fine  lines  around  the  margins  of 
the  teeth  which  were  then  reinserted  and  the  examination  begun. 
The  class  was  given  an  hour  and  a  half  to  polish  off  all  pencil  marks  with 
large  and  small  sticks  in  the  porte  polishers,  using  the  moistened  pumice 
on  them,  and  were  individually  marked  according  to  the  number  of 
pencil  marks  left  on  the  teeth,  three  points  being  deducted  from  one 
hundred  for  each  mark  found.  The  theoretical  examination  on  the 
system  of  polishing,  as  to  divisions,  surfaces,  hold  of  instrument,  ful- 
crum-points and  motion  was  held  over  for  the  next  lesson  on  account 
of  lack  of  time.  After  this  the  lessons  in  instrumentation  proceeded, 
as  per  schedule,  and  the  room  kept  open  as  before  for  practise.  The 
classes  had  access  to  the  mixture  of  plaster  and  varnish  to  put  on  the 
teeth  for  practise,  and  afterward  examinations  on  instrumentation 
were  held.  For  this  the  instructor  himself  had  the  plaster  and  varnish 
put  on  the  teeth,  as  nearly  as  possible  to  simulate  the  tartar  which 
naturally  accumulates  in  the  human  mouth,  and  allowed  it  to  harden. 
The  pupils  were  given  an  hour  and  a  half  for  removing  the  deposits 
with  the  instruments  and  polishers,  and  were  then  examined  upon 
their  knowledge  of  divisions,  teeth  involved,  surfaces,  proper  instru- 
ment to  use — grasp  of  the  instrument,  fulcrum-point  best  adapted, 
and  the  correct  motion. 

After  this  examination,  the  classes  were  considered  competent  to 
work  upon  the  mouths  of  children.  ^ 

This  work  [)roved  to  be  the  most  interesting  part  of  the  course  for 
several  reasons.  It  was  the  first  practical  application  of  theory  and 
practice  of  the  study  of  the  year,  and  the  enthusiasm  of  the  classes 
in  putting  their  studies  into  practical  use  and  the  apparent  desire 
evinced  by  the  children  from  all  walks  of  life  for  having  the  work  done 
and  their  mouths  treated,  was  inspiration  for  all.  Besides,  it  marked 
the  realization  of  an  ideal  of  the  instructor  and  his  assistant,  the  secre- 
tary of  the  course  of  training  of  dental  hygienists,  to  reach  and  treat 
a  large  nuniber  of  cliildren  with  whom  the  results  of  the  work  may  best 
be  realized. 

Application  blanks  were  prepared  and  sent  to  the  public  schools, 
orphan  asylums  and  organizations  of  boys'  clubs,  such  as  the  Boy 
Scouts,  and  when  ajji^lications  were  filed  with  the  secretary,  appoint- 
ments were  made  for  them  with  the  operators  (or  pupils  of  the  classes) 


Ph'ACTff'AL   COTJRSE  513 

filling  iij)  not  only  the  lesson  hours  of  Mondays,  Wechiesdays  and  Fri- 
days, but  for  the  practise  days  in  between,  Tuesdays,  Thursdays,  and 
even  Saturday  mornings — at  all  times  when  the  children  were  not 
otherwise  occupied  in  schools — so  that  when  the  lessons  upon  the  chil- 
dren were  begun,  the  operating  time  of  both  afternoon  and  evening 
classes  for  the  entire  two  weeks  to  be  devoted  to  the  children  was 
entirely  filled.  It  was  indeed  inspiring  when  the  classes  met,  to  have 
all  chairs  filled,  and  a  second  relay  of  children  w^aiting  in  the  impro- 
vised waiting-room.  Many  without  cards  came  on  the  chance  that 
they  might  be  taken  care  of. 

Every  child  was  requested  by  note  printed  on  the  appointment 
card,  to  bring  his  or  her  tooth-brush,  so  that  all  came  prepared  for  the 
lesson  in  brushing  that  each  operator  was  required  to  give  her  patient, 
the  operators  having  previously  been  taught  the  scientific  brushing  of 
the  teeth  and  gums  by  the  instructor.  This  lesson  served  the  double 
purpose  of  showing  the  children  the  proper  use  of  the  brush  for  future 
use  and  insuring  a  mouth  free  from  food  debris  upon  which  to  work. 

The  pupils  were  given  operating  blanks  upon  which  they  were 
required  to  note: 

1.  The  Angle  classification  of  occlusion. 

2.  The  number  of  temporary  teeth. 

3.  The  color  of  the  gums — dark  red,  light  red,  or  pink. 

4.  Location  of  cavities  in  permanent  teeth. 

5.  Fistulas. 

The  instructors  passed  from  chair  to  chair,  criticizing  the  work, 
correcting  the  charts,  and  instructing  on  special  points. 

As  each  pupil  operated  for  two  hours  every  day  excepting  Satur- 
days, and  for  at  least  one  session  on  Satiu^days,  over  five  hundred  chil- 
dren were  operated  on,  which  gave  each  pupil  a  great  deal  of  practise, 
to  say  nothing  of  the  benefit  to  the  children. 

Finally  examinations  were  held,  each  pupil  having  but  one  patient 
for  the  last  test  in  order  to  give  her  the  full  lesson  time  for  the  operation. 
For  this  75  per  cent,  was  allowed  for  perfection  in  operating  and  25 
per  cent,  for  correct  diagnosis  noted  upon  the  chart. 

The  next  lesson  began  the  last  part  of  the  practical  course,  the 
work  on  adult  patients.  The  secretary  sent  out  application  blanks, 
as  before,  this  time  to  the  factories  and  shops  and  drew  her  appli- 
cations for  appointments  from  among  the  young  women  employed 
in  them.  There  was  not  the  enormous  demand  for  this  work  that 
there  had  been  among  the  children,  although  more  than  enough 
applications  were  received  to  fill  all  of  the  pupils'  operating  time.  It 
was  strongly  emphasized,  in  sending  out  the  application  blanks  and 
later,  the  appointment  cards,  that  the  work  being  done  was  pm-ely 
educational  and  in  no  sense  one  of  charity,  the  principal  object  in  view 
being  the  teaching  of  the  benefits  of  clean  mouths,  showing  the  patients 
the  scientific  use  of  brush,  floss  and  wash — thoroughly  treating  their 
mouths,  taking  off  tartar  and  deposits  and  thoroughly  polishing  their 
33 


514  APPENDIX 

teeth,  in  the  hope  that  mouth  hygiene  would  not  only  be  of  lasting 
value  to  them,  but  might  be  spread  in  constantly  growing  circles. 

The  practise  of  the  pupils  was  not  lost  sight  of  as  the  work  progressed, 
the  instructor  examining  and  criticizing  as  before,  until  examinations 
were  held  and  final  marks  given  for  skill  in  handling  instruments  and 
polishers  and  for  thorough  cleaning  and  polishing  the  teeth  of  the 
patients  assigned. 

This  made  the  total  length  of  time  devoted  to  the  practical  course 
seven  weeks. 

SCHEDULE  OF  LESSONS  ON  MANIKINS. 

POLISHING   AND   INSTRUMENTATION. 
First. 

Teaching  the  four  motions — digital,  wrist,  rigid-arm,  and  rotary. 

Grasp  of  polishers. 

Direction  of  procedure  for  polishing. 

First  three  di\'isions  of  polishing. 
Second. 

Fourth,  fifth,  sixth,  seventh,  and  eighth  divisions. 
Third. 

Ninth,  tenth,  and  eleventh  divisions,  and  review  of  entire  labial  and  buccal  surfaces 
of  teeth  of  both  jaws. 
Fourth. 

Twelfth,  thirteenth,  fourteenth,  and  fifteenth  divisions. 
Fifth. 

Sixteenth  and  seventeenth  divisions  and  review  of  entire  lingual  surfaces  of  teeth  of 
both  jaws. 
Sixth. 

Beginning  instrumentation. 

First  two  divisions. 
Seventh. 

Third,  fourth,  fifth,  sixth,  seventh,  eighth,  and  ninth  divisions. 
Eighth. 

Practical  examination  on  polishing. 
Ninth. 

Theoretical  (half-hour)  examination  on  polishing. 

Review  of  instrumentation — removal  of  varnish  and  plaster  from  teeth  of  lower 
jaw. 

Divisions  ten  and  eleven. 
Tenth. 

Twelfth,  thirteenth,  fourteenth,  fifteenth,  sixteenth,  seventeenth,  and  eighteenth 
divisions  of  instrumentation. 
Eleventh. 

Review  instrumentation,  removal  of  varnish  and  plaster  from  teeth  of  upper  jaw. 

Divisions  nineteen  and  twenty. 

Use  of  floss  for  polishing  approximal  surfaces  and  use  of  brush  wheel  for  occlusal 
surfaces. 
Twelfth. 

Examination.     Instrumentation  (practical)  and  instrumentation  (theoretical). 

SYSTEM  FOR  INSTRUMENTATION. 

Division  1.     Fig.  1.38. 

Teeth.  Right  lower  molars,  bicuspids,  cuspid,  lateral,  and  central. 

Surface.  Lingual. 

Instrument.  No.  18  Darby-Perry. 

Grasp.  Pen-holder. 

Fulcrum-point.     End  of  third  finger  between  left  lower  cuspid  and  bicuspid  on 

occlusal  surface. 
Motion.  Wrist  or  rotary. 


SYSTEM  FOR  INSTRUMENTATION  515 

Division  2.     Figs.  139  and  140. 

Teeth.  Left  lower  central,  lateral,  cuspid,  bicuspids,  and  molars. 

Surface.  Lingual. 

Instrument.  No.  17  Darby-Perry. 

Grasp.  Pen-holder. 

Fulcrum-point.     End  of  second  finger  on  cutting  edge  of  right  lower  cuspid  or 

lateral  for  left  lower  central,  lateral,  and  cuspid. 
End   of   third    finger   on    cutting   edge   of   lower   centrals    for 

bicuspids  and  molars. 
Motion.  Rotarj\ 

Division  3.     Fig.  141. 

Teeth.  Left  lower  molars,  bicuspids,  and  cuspid. 

Surface.  Buccal. 

Instrument.  No.  18  Darby-Perry. 

Fulcrum-point.     End  of  third  finger  on  labial  surface  of  lower  incisors. 

Motion.  Wrist  or  rotary. 

Division  If.     Figs.  142  and  143. 

Teeth.  Lower  incisors,  right  lower  cuspid,  bicuspids,  and  molars. 

Surface.  Labial  and  buccal. 

Instrument.  No.  17  Darby-Perry. 

Grasp.  Pen-holder. 

Fulcrum-point.     End  of  second  or  third  finger  between  left  lower  cuspid  and 
bicuspid  for  lower  incisors. 
Advanced  on  incisors  for  cuspid,  bicuspids,  and  molars. 
Motion.  Rotary. 

Dioision  5.     Figs.  144  and  14.5. 

Teeth.  Right  lower  molars,  bicuspids,  and  cuspid. 

Surface.  Distal. 

Instrument.  No.  13  Smith  set. 

Grasp.  Pen-holder. 

Fulcrum-point.     End  of  third  finger  on  cutting  edge  of  lower  incisors  for  distal 

surface  of  last  molar. 
End  of  third  finger  on  labial  surface  of  right  cuspid  and  incisors 

for  the  balance. 
Motion.  Wrist  and  digital. 

Division  6.     Similar  to  Figs.  144  and  145. 

Teeth.  Left  lower  cuspids,  bicuspids,  and  molars. 

Surface.  Distal. 

Instrument  No.  13  Smith  set. 

Grasp.  Pen-holder. 

Fulcrum-point.  End  of  third  finger  on  labial  surface  of  lower  incisors. 

Motion.  Wrist  and  digital. 

Division  7.     Similar  to  Fig.  146. 

Teeth.  Right  lower  molars,  bicuspids,  and  cuspid. 

Surface.  Mesial. 

Instrument.  No.  14  Smith  set. 

Grasp.  Pen-holder. 

Fulcrum-point.  End  of  third  finger  on  labial  surface  of  right  cuspid  and  incisors. 

Motion.  Wrist  and  digital. 

Division  8.     Fig.  146. 

Teeth.  Left  lower  cuspid,  bicuspids,  and  molars. 

Surface.  Mesial. 

Instrument.  No.  14  Smith  set. 

Grasp.  Pen-holder. 

Fulcrum-point.  End  of  third  finger  on  labial  surface  of  lower  incisors. 

Motion.  Wrist  and  digital. 


516  APPENDIX 

Division  9.     Fig.  147. 

Teeth.  Lower  incisors. 

Surface.  Approximal. 

Instrument.  Nos.  5  and  6  Smith  set. 

Grasp.  Pen-holder. 
Fulcrum-point.     Third  finger  on  chin. 

Motion.  Wrist. 

Division  10.     Fig.  148. 

Teeth.  Right  upper  molars,  bicuspids,  cuspid,  lateral,  and  central. 

Surface.  Lingual. 

Instrument.  No.  17  Darby-Perry. 

Grasp.  Pen-holder. 

Fulcrum-point.     End  of  third  finger  on  occlusal  surface  between  left  lower  cuspid 

and  bicuspid. 
Motion.  Wrist. 

Division  11.     Figs.  149  and  150. 

Teeth.  Left  upper  central,  lateral,  cuspid,  bicuspids,  and  molars. 

Surface.  Lingual. 

Instrument.  No.  18  Darby-Perry. 

Grasp.  Pen-holder. 

Fulcrum-point.     End  of  second  finger  on  cutting  edge  of  right  upper  cuspid. 

Motion.  Rotary. 

Division  12.     Fig.  151. 

Teeth.  Left  upper  molars,  bicuspids,  cuspid,  lateral,  and  central. 

Surface.  Buccal  and  labial. 

Instrument.  No.  17  Darby-Perry. 

Grasp.  Pen-holder. 

Fulcrum-point.     End  of  second  finger  on  labial  surface  of  left  upper  central  and 

lateral   and  end  of  third   finger  on  lingual  surface  of  right 

upper  central  and  lateral,  for  molars,  bicuspids,  and  cuspid. 

End  of  third  finger  on  cutting  edge  of  right  upper  cuspid  for 

lateral  and  central. 

Motion.  Rotary. 

Division  13.     Fig.  152. 

Teeth.  Right  upper  central,  lateral,  cuspid,  bicuspids,  and  molars. 

Surface.  Labial  and  Buccal. 

Instrument.  No.  18  Darby-Perry. 

Grasp.  Pen-holder. 

Fulcrum-point.  Back  of  third  and  fourth  finger  on  chin. 

Motion.  Rigid-arm  and  rotary. 

Division  H.     Fig.  153. 

Teeth.  Right  upper  molars,  bicuspids,  and  cuspid. 

Surface.  .  Distal. 

Instrument.  No.  13  Smith  set. 

Grasp.  Pen-holder. 

Fulcrum-point.     End  of  second  or  third  finger  on  labial  surface  of  lower  incisors. 

Motion.  Digital  and  wrist. 

Division  15.     Similar  to  Fig.  153. 

Teeth.  Left  upper  cuspid,  bicuspids,  and  molars. 

Surface.  Distal. 

Instrument.  No.  13  Smith  set. 

Grasp.  Pen-holder. 

Fulcrum-point.  I'.nd  of  second  or  third  finger  on  labial  surface  of  lower  incisors. 

Motion.  Digital  and  wrist. 

Divviion  KL     Similar  to  Fig.  153. 

Teeth.  Right  upper  molars,  bicuspids,  and  cuspid. 

Surface.  Mesial. 

Instrument.  No.  14  Smith  set. 

Grasp.  Pen-holder. 

Fulcrum-point.  End  of  second  or  third  finger  on  labial  surface  of  lower  incisors. 

Motion.  Digital  and  wrist. 


SYSTEM  FOR  POLISHING  517 

Division  17.     Similar  to  Fig.  153. 

Teeth.  Loft  upper  cuspid,  bicuspid.s,  and  molars. 

Surface.  Mesiiil. 

Instrument.  No.  14  Snuth  set. 

Grasp.  Pen-holdur. 

Fulcrum-point.  End  of  second  or  third  finger  on  labial  surface  of  lower  incisors. 

Motion.  Digital  and  wrist. 

Division  18.     Similar  to  Fig.  147. 

Teeth.  Upper  incisors. 

Surface.  Approximal. 

Instrument.  Nos.  5  and  6  Smith  set. 

Grasp.  Pen-holder. 

Fulcrum-point.  Back  of  third  or  fourth  finger  on  chin. 

Motion.  Wrist  and  digital. 

Division  10.     Fig.  154. 

Teeth.  Lower. 

Surface.  Buccal,  labial,  and  lingual. 

Instrument.  Sickle-shaped. 

Grasp.  Pen-holder. 

Fulcrum-point.  End  of  second  or  third  finger  on  cutting  edge  of  incisors. 

Motion.  Digital.     Draw  stroke. 

Division  20.     Fig.  155. 

Teeth.  Upper. 

Surface.  Buccal,  labial,  and  lingual. 

Instrument.  Sickle-shaped. 

Grasp.  •      Pen-holder. 

Fulcrum-point.     Back  of  third  or  fourth  finger  oh  chin;     or  fist  grasp — end  of 

thumb  on  occlusal  surface. 
Motion.  Digital.     Draw  stroke. 

Division  21. 

Instrument.  Nos.  3  and  4  Harlan. 

Use  For  small,  hard,  tenacious  deposits  under  gingival  border. 

Motion.  Draw  stroke. 

SYSTEM  FOR  POLISHING -LARGE  STICK. 

Division  1.     Fig.  158. 

Teeth.  Upper  right  central  and  lateral. 

Surface.  Labial. 

Grasp.  Porte  polisher  held  in  fist. 

Fulcrum-point.     End  of  thumb  on  cutting  edge  of  right  cuspid. 

Motion.  Digital. 

Division  2.     Fig.  159. 

Teeth.  Upper  right  cuspid,  first  and  second  bicuspids. 

Surface.  Labial. 

Grasp.  Fist. 

Fulcrum-point.     Back  of  third  finger  on  chin. 

Motion.  Rigid-arm. 

Division  3.     Fig.  160. 

Teeth.  Upper  right  molars. 

Surface.  Buccal. 

Grasp.  Pen-holder. 

Fulcrum-point.     Back  of  third  or  fourth  finger  on  chin. 

Motion.  Rotary. 

Division  J^:    Similar  to  Fig.  160. 

Teeth.  Lower  right  molars. 

Surface.  Buccal. 

Grasp.  Pen-holder. 

Fulcrum-point.     Back  of  third  or  fourth  finger  on  chin. 

Motion.  Rotary. 


518  APPENDIX 

Dinsion  5.     Similar  to  Fig.  159. 

Teeth.  Lower  right  bicuspids  and  cuspid. 

Surface.  Buccal. 

Grasp.  Fist. 

Fulcrum-point.     Back  of  third  finger  on  chin. 

Motion.  Rigid-arm. 

Division  6.     Fig.  161. 

Teeth.  Lower  incisors. 

Surface.  Labial. 

Grasp.  Fist. 

Fulcrum-point.     Thumb  or  first  finger  of  left  hand,  depressing  lips. 

Motion.  Rigid-arm. 

Division  7.     Similar  to  Fig.  159. 

Teeth.  Left  lower  cuspid  and  bicu.spid. 

Surface.  Labial. 

Grasp.  Fist. 

Fulcrum-point.     Back  of  third  finger  on  chin. 

Motion.  Rigid-arm. 

Division  8.     Similar  to  Fig.  162. 

Teeth.  Lower  left  molars. 

Surface.  Buccal. 

Grasp.  Pen-holder. 

Fulcrum-point.     Back  of  third  or  fourth  finger  on  chin. 

Motion.  Rigid-arm. 

Division  'J.     Fig.  162. 

Teeth.  Upper  left  molars. 

Surface.  Buccal. 

Grasp.  Pen -holder. 

Fulcrum-point.     Back  of  third  or  fourth  finger  on  chin. 

Motion.  Rigid-aim. 

Division  10.     Similar  to  Fig.  159. 

Teeth.  Left  upper  bicuspids  and  cuspid. 

Surface.  Labial. 

Gra.sp.  Fist. 

Fulcrum-point.     Back  of  third  or  fourth  finger  on  chin. 

Motion.  Rigid-arm.  , 

Division  11.     Similar  to  Fig.  158. 

Teeth.  Left  upper  lateral  and  central. 

Surface.  Labial. 

Grasp.  Fist. 

Fulcrum-pf)iiit.     End  of  tlminl)  on  cutting  edge  of  right  central. 

Motion.  Digital. 

Division  12.     Fig.  103. 

Teeth.  Right  lower  molars  and  bicuspids. 

Surface.  Lingual. 

Grasp.  Pcn-h(jlder. 

Fulcrum-point.     Back  of  third  or  fourth  finger  on  chin. 

Motion.  Rotary  (or  using  side  of  stick  with  rigid-arm  motion). 

Division  13.     Fig.  164. 

Teeth.  Right  lower  cuspids  and  incisors. 

Surface.  Lingual. 

Grasp.  Pen-holder. 

Fulcrum-point.      lOnd  of  second  or  third  finger  from  cutting  edge  of  incisors  to 

first  bicuspid. 
Motion.  Rotary. 


SYSTEM  FOR  POLISHING  519 

Division  Iff.     Fig.  105. 

Teeth.  Left  lower  cuspid,  bicuspids,  and  molars. 

Surface.  Lingual. 

(Jrasp.  Pen-holder. 

Fulcrum-point.     lOnd  of  second  finger  on  labial  surface  of  lower  incisors. 

Motion.  Both  rigid-arm  and  rotary. 

Division  15.     Fig.  166. 

Teeth.  Left  uj^per  molars  and  bicuspids. 

Surface.  Lingual. 

Grasp.  Pen-holder. 

Fulcrum-poin.t.     End  of  third  finger  on  labial  surface  of  right  lower  lateral  or 

cuspid. 
Motion.  Rigid-arm  (or  third  finger  on  masticating  surface  of  right  upper 

bicuspid,  rotary  motion). 

Division  16.     Fig.  107. 

Teeth.  Left  upper  cuspid  and  upper  incisors. 

Surface.  Lingual. 

Grasp.  Pen-holder. 

Fulcrum-point.     End  of  second  or  third  finger  on  cutting  edge  of  right  upper 

cuspid. 
Motion.  Rotary. 

Division  17.     Fig.  168. 

Teeth.  Right  upper  cuspid,  bicuspids,  and  molars. 

Surface.  Lingual. 

Grasp.  Pen-holder. 

Fulcrum-point.     Back  of  third  or  fourth  finger  on  chin. 

Motion.  Rotary. 


INDEX. 


Abscess,  alveolar,  209 

dental  pulp  in,  272 
treatment  of,  279 
x-rays  in,  281 

definition  of,  165 

pericemental,  27G 

treatment  of,  277 
Absorption,  physiology  of.  111 
Acne,  408 
Adenitis,  416 
Adenoids,  24 

Adipose  tissue,  structure  of,  41 
Air  cells,  anatomy  of,  63 

ethmoidal,  anatomy  of,  63 
mastoid,  anatomy  of,  64 

changes  in,  physiology  of,  116 

sacs,  anatomy  of,  32 
Albuminoids,  physiology  of,  106 
Alimentary  sj^stem,  anatomy  of,  23 

tract  in  dental  prophylaxis,  292 
Alimentation,  physiology  of,  106,  108 
Alopecia,  414 

areata,  415 
Alveolar  abscess,  269 

dental  pulp  in,  272 
treatment  of,  279 
x-rays  in,  281 

process,  81,  100 
Alveoli,  structure  of,  32 
Alveolus,  81 

Ameba,  physiology  of,  105 
Amylopsin,  110 
Anabolism,  105 

Angle's  classification  of  malocclusion,  246 
Anterior  fossa  of  skull,  59 

lacerated  foramen,  59 

nares,  62 

palatine  fossa,  61 
Antitoxins,  definition  of,  139,  147,  149 

making  of,  technic  of,  149 
Antra  of  Highmore,  anatomy  of,  63 
Anus,  anatomy  of,  27 
Aorta,  34 

Apical  foramen,  80 
Appendicular  skeleton,  44 
Aqueous  humor,  anatomy  of,  66 
Arachnoid,  structure  of,  53 
Areolar  tissue,  structure  of,  41 
Arteries,  anatomy  of,  34 

carotid,  35 


Arteries,  coronary,  34 

iliac,  35 

innominate,  35 

mesenteric,  35 

physiology  of,  119 

renal,  35 

subclavian,  35 
Arterioles,  119 
Artery,  hepatic,  28 

maxillary,  internal,  anatomy  of,  77 

pulmonary,  anatomy  of,  34 
phj^siology  of,  120 
Articulation,  temporomaxillarj',  anatomy 

of,  73 
Ascending  colon,  26 
Assimilation,  physiology  of,  112 
Auditory  canal,  external,  67 

meatus,  external,  67 

nerve,  54 
Auricles,  physiology  of,  118 
Axial  skeleton,  44 
Axon,  50 


B 


Baboox,  teeth  of,  214 
Bacillus,  definition  of,  132 
Bacteria,  artificial  cultivation  of,  134 

classification  of,  131 

colonies  of,  definition  of,  134 

description  of,  131 

fiagella  of,  136 

motility  of,  136 

non-pathogenic,  137 

pathogenic,  138 

paths  of  infection  of,  139 

propagation  of,  133 

relation  of,  to  disease,  137 
Bacterial  diseases  of  skin,  407 

poisons,  146 

propagation  and  dental  propliylaxis, 
295 
Bacteriology',  142 
Ball-and-socket  joints,  46 
Bicuspids,  anatomy  of,  84 

individual  characteristics  of,  84 

occlusion  of,  224 
Bile  ducts,  29 

common,  29 

salts,  110 
Birth-marks,  415 
Black  bear,  teeth  of,  211 


522 


JXDEX 


Bladder,  anatomv  of,  38 

dotting  of,  il8 
Blood  corpuscles,  35 

normal,  constituents  of,  159 

physiology-  of,  117 

plasma,  35 

definition  of,  160 
phj'siologj'  of,  118 

platelets,  159 

phj-siology  of,  118 

structure  of,  35 

supply  of  dental  tissues,  75 
Bloodvessels,  anatomy  of,  34 

physiolog>-  of,  119 

of  pxilp,  93 

of  skin,  41 
Bodv,  resistive  forces  of,  lengthening  the 

life  of.  449 
Boils,  409 
Bones,  44 

of  head,  44 

of  lower  extremity,  45 

maxillary,  anatomy  of,  70,  72 

palate,  anatomy  of,  72 

of  spinal  column,  45 

of  thorax,  45,  115 

of  upper  extremity',  45 
Bony  sinuses,  anatomy  of,  63 
Bowman's  capsule,  38 

disks,  48 
Brain,  structure  of,  53 

ventricles  of,  structm'e  of,  54 
Bronchi,  anatomy  of,  32 

physiology  of,  115 
Bronchioles,  32 

phj^siology  of,  115 
Brushing  of  teeth  in  dental  prophj^laxis, 
339 


Canal,  auditor}',  external.  67 
Canals,  semicircular,  anatomy  of,  70 
Capillaries,  anatomj'  of,  35 

physiology^  of,  119 
Capsular  ligament,  219 
Capsule  of  Tenon,  64 
Carbohydrates,  composition  of,  368 

physiology  of,  106 
Carbon  dioxide,  physiology  of,  112 
Carbuncle,  409 
Cardiac  muscles,  47 

valves  of  stomach,  24 
Caries,  dental,  187,  237 
Carnivorous  animals,  teeth  of,  210 
Carotid  arteries,  35 
Cartilage,  anatomy  of,  19 

structure  of,  43 
Catarrhal  inflammation,  definition  of,  158 
Cecum,  26 
Cell,  20,  104 

life,  factors  for,  290 

membrane,  21 

nerve,  function  of,  125 

nucleus  of,  21 


Cell,  structure  of,  20 

wall,  21 
Cells,  ail',  anatomy  of,  63 
ethmoidal,  63 
mastoid,  64 

endothelial,  functions  of,  160 

nerve,  50 

of  pulp,  connective-tissue,  93 
Cement  oblasts,  93,  98 
Cementum,  anatomj^  of,  80 

functions  of,  93 

histology  of,  91 

lacunte  of,  92 

lamellae  of,  91 
Cerebellum,  function  of,  128 

structure  of,  54 
Cerebrum,  function  of,  129 

structure  of,  53 
Cheeks,  anatomy  of,  74 
Chemistry  of  food,  367 

of  nutrition,  367 
Chest  wall,  structure  of,  33 
Chicken-pox,  418 
Choana?,  62 
Chordse  tendonae,  48 
Choroid,  66 

Chyle,  phj'siologj' of,  111 
Ciliary  body,  65 

muscle,  65 

processes,  65 
Circulation,  h'mphatic,  physiology  of,  121 

normal,  159 

phj'siology  of ,  117 

portal,  physiology  of,  121 

sj'stemic,  physiology'  of,  121 
Cu'culatory  system,  anatomy  of,  33 

tissue,  19 
Circumvallate  papilla?  of  tongue,  74 
Coccus,  definition  of,  132 
Cochlea,  anatomy  of,  69 
Cock's  crest,  59 
Colon,  ascending,  26 

descending,  26 

sigmoid  flexure  of,  27 

transverse,  26 
Congenital  syphilis,  425 
Connective-tissue  cells  of  pulp,  93 

function  of,  160 

structure  of,  43 
Coronal  sutures,  57 
Coronary  arteries,  34 
Corpus  callosum,  structure  of,  54 
Corti,  organ  of,  69 
Cranial  nerves,  anatomy  of,  75,  77 
Cranium,  anatomy  of,  57 
Crista  galli,  59 
Crocodiles,  teeth  of,  207 
Cross-striated  muscles,  47 
Crystalline  lens,  anatomy  of,  66 
Curve  of  Spec,  225,  226 
Cuspids,  anatomy  of,  82 
Cuticle,  40 

Cutis,  structure  of,  41 
Cystic  duct,  29 
Cytoplasm,  21,  104 


INDEX 


523 


Deciduous  teeth,  anatomy  of,  87 

eruption  of,  88 
Dental  caries,  187,  237 

areas  of  immunity  to,  237 

of  susceptibility  to,  237 
disuse  of  teeth  as  cause  of,  257 
lactic  acid  in,  197 
malocclusion  and,  238 
saliva  in,  196 
symptoms  of,  196 
hygiene,  course  in,  practical,  510 
theoretical,  505 
in  public  schools,  483 

class-room     talks     in, 

497 
equipment  for,  490 
hours  of  employment 

in,  492 
law  relating  to,  485 
limit  of  service  in,  485 
location  of  schools  and, 

490 
organization  in,  485 
parents'      cooperation 

in,  500 
stereopticon  lectures 

and,  502 
sterilization  in,  496 
supervisors  in,    487 
teachers'    cooperation 

in,  500 
tooth-brush   drills   in, 

-.97 
use   of   dental   engine 

in,  496 
use  of  tooth-brushes  in 
496 
prophylaxis,  288 

alimentary  tract  in,  292 
bacterial  propagation  in,  295 
brushing  in,  339 

of  buccal  surfaces,  347 
instructions  for,  347 
of  labial  surfaces,  347 
of  lingual  sm-faces,  349 
of  masticating  surfaces,  352 
number  of  daily,  353 
in  children,  338 

decomposing  food  debris  in,  293 
dentifrices  in,  354 
field  of  service  in,  300 
floss  silk  in,  355 
gums  in,  341 
instrumentation  in,  304,  313 

four  motions  in,  309 
instruments  in,  309 
keratin  in,  340 
lime-water  in  358 
of  lower  jaw,   instrumentation 

in,  309 
polishing  in,  326 

brush  wheel  in,  337 
floss,  336 


Dental  prophylaxis,  polishing  in,  system 
of,  328 
practical  work  of,  302 
principles  of,  299 
pyorrhea  alveolaris  and,  298 
summary  of,  361 
surfaces  of  teeth  in,  304 
syphilis  and,  298 
system  of,  365 
systemic  infection  and,  298 
the  cell  in,  288 
tissue  stimulation  in,  341 
tooth-brushes  and,  345 
tuberculosis  and,  297 
of  upper  jaw,  instrumentation 
in,  320 
tissue,  blood  supply  of,  75 
nerve  supply  of,  75 
Dentifrices,  use  of,  in  dental  prophylaxis, 

354 
Dentin,  anatomy  of,  80 
function  of,  91 
histology  of,  90 
matrix  of,  91 
secondary,  94 
Dentinal  tubules,  91 
Dentistry,  institutional,  463 
foreword  on,  463 
versus    infectious    diseases     of 
childhood,  464 
Derma,  401 
Dermatitis,  definition  of,  402 

venenata,  409 
Dermis,  physiology  of,  123 
Descending  colon,  26 
Diaphragm,  33 

physiology  of,  115 
Digastric  muscle,  218 
Digestion,  physiology  of,  106 
Disaccharides,  definition  of,  370 
Disinfection,  153 

methods  of,  154 
Dog,  teeth  of,  212 
Drum  of  ear,  anatomy  of,  67 
Ductless  glands,  structure  of,  41 
Duodenum,  26 
Dura  mater,  structure  of,  53 


E 


Ear,  external,  anatomy  of,  67 

internal,  anatomy  of,  68 

middle,  anatomy  of,  67 

ossicles,  anatomy  of,  67 
Ears,  nerve  supply  of,  70 
Eczema,  416 

acute,  416 

chronic,  416 
Edema,  definition  of,  164,  402 
Ehrlich's  side-chain  theory  of  immunity, 

151 
Elastic  tissue,  19 
Elephant,  teeth  of,  217 
Enamel,  anatomy  of,  80 


524 


INDEX 


Enamel,  functions  of,  90 

histology  of,  88 
Endolyniph,  69 
Endothelial  cells,  function  of,  160 

leukocytes,  definition  of,  160 
Enzj-mes,  143 

properties  of,  108  /^ 

Epidermis,  401 

function  of,  123 

tissue,  40 
Epiglottis,  30 

physiology  of,  114 
Epithelial  tissue,  19 
Erysipelas,  409 
Erj'thema,  definition  of,  402 

multiforme,  411 

nodosum,  411 
Esophagus,  anatomy  of,  24 
Ethmoidal  air  cells,  anatomy  of,  63 
Eustachian  tube,  anatomj'  of,  68 
Exanthema,  infectious,  definition  of,  417 
Excretion,  physiology  of,  122 
Excretory  system,  anatomy  of,  37 
Exercises  and  h3'giene,  434 
External  auditory  canal,  67 

meatus,  67 
Exudation,  definition  of,  164 
Exudative    inflammation,  definition  of, 

158 
Eyeball,  anatomy  of,  66 
Eyes,  anatomy  of,  64 

coats  of,  64 
fibrous,  64 
nervous,  66 
vascular,  64 

refracting  media  of,  66" 


Face,  anatomy  of,  61 
Facial  nerve,  anatomj^  of,  77 
Fascia,  50 
Fats,  composition  of,  368 

physiology  of,  107,  111,  112 
Fauces,  anatomy  of,  78 
Fermentation,  definition  of,  144 
Ferments,  143 
Fever  blisters,  413 

sores,  413 
Fibriike,  48 
Fibrinogen,  35 

l'"ibrinous  exudation,  definition  of,  104 
Fibroblasts,  98 

Fifth  cranial  nerve,  anatomy  of,  75 
Fishes,  tr-cth  of,  200 
Fissure,  sphenoidal,  59 
Fissures  sphenomaxillary,  01 
Fistula,  definition  of,  166 
Flagellaof  bacteria,  136 
Floss  silk,  use  of,  in  dental  prophylaxis, 

355 
Food,  chemistry  of,  367 

materials,  chemical  composition  of,  369 
Foods,  nitrogenous,  physiology  of,  100 


Foods,  non-nitrogenous,   physiology  of, 

106 
Foramen,  lacerated,  anterior,  59 
middle,  59 
optic,  59 
ovale,  59 
rotundiun,  59 
Fossae,  nasal,  anatomy  of,  62 
palatine,  anterior,  61 

posterior,  61 
of  skull,  anterior,  59 
middle,  59 
posterior,  59 
zj'gomatic,  61 
Frenum,  74 
Frogs,  teeth  of,  207 
Frontal  sinuses,  anatomy  of,  63 
Fuel  value  of  daily  food,  table  of,  388 
Fundus  of  stomach,  24 


G 


Gall-bladder,  29 

Ganglia,  50 

Gastric  digestion,  physiology  of,  109 

glands,  25 

juice,  physiology  of,  109 
Geniohj^oicl  muscle,  218 
German  measles,  418 
Germination,  definition  of,  134 
Glands,  ductless,  structure  of,  41 

gastric,  25 

oil,  structure  of,  41 

parathyroid,  structure  of,  42 

parotid,  anatomy  of,  78 

salivary,  anatomy  of,  27,  77 
physiology  of,  108 

sebaceous,  physiology  of,  123 

sublingual,  anatomy  of,  78 

submaxillary,  anatomy  of,  78 

sweat,  anatomy  of,  41 
physiology  of,  123 

thymus,  structure  of,  42 

thyroid,  structure  of,  42 
Glandular  tissue,  19 
Glenoid  fossa,  61 
Gliding  joints,  46 
Glottis,  30 

Granular  layer  of  Tomes,  91 
Gummata  of  mouth,  426 

of  throat,  426 

of  tongue,  426 
Gums,  81 

care  of,  in  dental  prophylaxis,  341 
Gyrate,  definition  of,  403 


H 


Hard  palate,  anatomy  of,  74 
Head,  bones  of,  44 

Healing  by  first  intention,  definition  of, 
167 


INDEX 


525 


Healing  by  second  intention,  definition 

of,  108 
Heart,  anatomy  of,  33 
physiology  of,  US 
Heat  energy,  supply  of,  373 
Hemoglobin,  35 
Hepatic  artery,  28 

duct,  29 
Hereditary  syjihilis,  425 
Herpes,  413 

lliglnnore,  antra  of,  anatomy  of,  63 
Hinge  joints,  46 

sliding,  47 
Hives,  412 
Hormones,  41 
Horse,  teeth  of,  217 
Hutchinson's  teeth,  426 
Hygiene,  142 

deep  breathing  and,  443 
dental,  course  in,  practical,  510 
theoretical,  505 
in  public  schools,  483 

class-room     talks     in, 

497 
equipment  for,  490 
hours  of  employment 

in,  492 
law  relating  to,  485 
limit  of  service  in,  485 
location  of  schools,  490 
organization  in,  485 

supervisors  in,  487 
parents'  cooperation  in, 

500 
stereopticon     lectures 

and,  502 
sterilization  in,  496 
teacher's    cooperation 

in,  500  • 

tooth-brush  drills    in, 

497 
use  of    tooth-brushes 
in,  496 
exercises  and,  educational,  434 

hygienic,  434 
fresh  air  and,  440 
immobility  and,  432 
instruction  in,  431,  435 
mouth,  teaching  of,  to  school  chil- 
dren, 459 
what  it  can  do,  467 
what  it  has  done,  467 
objective,  431 

personal,  children  in  schools  and,  430 
daily  routine  in,  437 
environment  in,  429 
factors  in,  429 
race  death  in,  429 
teaching  and,  430 
physical  training  and,  434 
posture  and,  435 
racial,  429 
subjective,  431 
Hyperemia,  definition  of,  163 
Hypophysis,  structure  of,  42 


Ileocecal  valve,  26 
Ileum,  26 
Iliac  arteries,  35 
Immovable  joints,  46 
Immunity,  acquired,  147 

definition  of,  147,  150 

natural,  147 

theories  of,  150 

Ehrlich's  side-chain,  151 
Impetigo  (iontagiosa,  407 
Incisors,  anatomy  of,  81 
Indian  tiger,  teeth  of,  211 
Infectious  exanthemata,  definition  of,  417 
Inferior  maxillary  bone,  anatomy  of,  72 
Inflammation,  acute,  definition  of,  162 

causes  of,  160 

chronic,  definition  of,  166 

classification  of,  158 

definition  of,  158 

forms  of,  158 

injurious  agent  in,  160 

injury  in,  162 
Infundibula,  115 
Injury,  definition  of,  162 
Innominate  artery,  35 
Inorganic  salts,  composition  of,  368 
Institutional  dentistry,  463 
Intercellular  substances,  21 

of  pulp,  93 
Intercostal  muscles,  33 
Intercostals,  115 

Internal  maxillary  artery,  anatomy  of,  77 
Interproximal  spaces,  238 
Interstitial  inflammation,  definition  of,  158 
Intestinal  tract,  histology  of,  29 
Intestine,  large,  anatomy  of,  26 

small,  anatomy  of,  28 
physiology  of,  110 
viUi  of,  26 
Iris,  anatomy  of,  65 
Islands  of  Langerhans,  27 
Itch,  406 
Ivy  poisoning,  409 


Jaws,  development  of,  103 
Joints,  ball-and-socket,  46 

gliding,  46 

hinge,  46 

immovable,  46 

movable,  46 

pivot,  46 

saddle,  46 

sliding  hinge,  47 

slightly  movable,  46 

structure  of,  46 

torsional,  46 


Keratin,  use  of,  in  dental  prophylaxis, 

340 
Kidneys,  physiology  of,  123 
structure  of,  37 


526 


INDEX 


L.^BYRiNTH,  anatomy  of,  68 
Lacerated  foramen,  anterior,  59 

middle,  59 
Lachn-mal  apparatus,  anatomy  of,  67 
Lactic  acid  in  dental  caries,  197 
Lacunae  of  cementum,  92 
Lambdoid  sutm-es,  57 
Lamellae  of  cementum,  91 
Langerhans,  Islands  of,  27 
LarjTix,  anatomy  of,  30 

phj'siology  of,  114 
Lemurs,  teeth  of,  217 
Lens,  crystalline,  anatomy  of,  66 
Lesion,  definition  of,  162 
Leukocytes,  36 

endothelial,  definition  of,  160 

mononuclears,  definition  of,  160 

physiolog>'  of,  117 

polymorphonuclear,   definition   of, 
159 
Leukoplakia,  definition  of,  427 
Ligament,  capsular,  219 

sphenomandibular,  219 

stylomandibular,  219 
Ligaments,  anatomy  of,  19 

structure  of,  43 
Lime-water,  use  of,  in  dental  prophylaxis, 

358 
Lingual  tonsil,  74 

anatomy  of,  78 
Lips,  anatomy  of,  74 
Liver,  anatomy  of,  28 

physiology  of,  110 
Louse,  body,  405 

head,  405 

pubic,  406 
Lower  extremity,  bones  of,  45 
Lungs,  anatomy  of,  32 

physiology  of,  115,  122 
Lymph  glands,  37 

nodes,  37 
Lymphatic  circulation,  physiology  of ,  121 
Lymphatics,  anatomy  of,  36 
Lymphocytes,  definition  of,  160 

M 

Macula  lutea,  66 
Macule,  definition  of,  402 
Malocclusion  of  teeth,  237 

and  dental  caries,  238 
classification  of,  245 

Angle's,  246 
definition  of,  244 
etiolog>'  of,  251 

(extraction    of    permanent 

teeth,  252 
lack  of  use  and,  253 
pernicious  habits  and,  252 
prtemature  loss  of  decidu- 
ous teeth  and,  252 
growth  of  jaws  in,  253 
mdividual,  244 
pyorrhea  alveolaris  and,  262 


Malpighi,  pyramids  of,  37 
Malpighian  corpuscles,  124 
Mandible,  anatomy  of,  72 

muscles  of,  anatomy  of,  73 
Masseter  muscles,  218 
Mast  cells,  definition  of,  160 
Mastication,  muscles  of,  218 

physiology  of,  108 
Mastoid  air  cells,  anatomy  of,  64 

antrum,  anatomy  of,  68 
Maxillary  artery,  internal,  anatomy  of, 
77 

bones,  anatomy  of,  70,  72 

sinuses,  anatomy  of,  63 
Measles,  417 

German,  418 
Meatus,  auditory,  external,  67 
Medulla  oblongata,  structure  of,  54 
Mesenteric  artery,  35 
Metabolism,  105 

chemical  changes  of,  371 
Micrococcus,  definition  of,  132 
Middle  fossa  of  skull,  59 

lacerated  foramen,  59 
Mineral  salts,  physiology  of,  107 
Molars,  lower,  anatomy  of,  86 

occlusion  of,  224 

upper,  anatomy  of,  84 

individual  characteristics  of,  86 
Monkeys,  teeth  of,  213 
Mononuclear  leukocytes, definitionof,  160 
Monosaccharides,  definition  of,  370 
Motility  of  bacteria,  136 
Motor  system,  structure  of,  47 

tissue,  20 
Mouth,  anatomy  of,  24,  70 

gummata  of,  426 

hygiene  of,  teaching  of,   to  school 
children,  459 
what  it  can  do,  467 
what  it  has  done,  467 

as  path  of  infection,  141 
Movable  joints,  46 
Muscles,  cardiac,  47 

ciliary,  65 

cross-striated,  47 

diagastric,  218 

geniohyoid,  218 

intercostal,  33 

of  mandible,  anatomy  of,  73 

masseter,  218 

of  mastication,  218 

mylohyoid,  218 

non-striated,  47 

pterygoid,  218 

of  skin,  41 

smooth,  48 

temi)oral,  218 
Muscular  system,  structure  of,  47 
Mylohyoid  muscle,  218 


N 


Narrr,  anterior,  62 
posterior,  62 


INDEX 


527 


Nasal  fossae,  anatomy  of,  62 

passages,  jjliysiology  of,  114 
septum,  62 
Nasmytli's  membrane,  90 
Necrosis,  definition  of,  162 
Nerve  cells,  50 

function  of,  125 
cranial,  fifth,  anatomy  of,  75 
seventh,  anatomy  of,  77 
endings,  structure  of,  56 
facial,  anatomy  of,  77 
fibers,  function  of,  125 
receptive  organs  of,  function  of,  125 
supply  of  dental  tissues,  75 
trifacial,  anatomy  of,  75 
Nerves,  auditory,  54 
olfactory,  54 
optic,  54 

j)neumogastric,  54 
of  pulp,  94 
of  skin,  41 
vagus,  54 
Nervous  system,  central,  physiology  of, 
127 
physiology  of,  125 
structure  of,  50 

sympathetic,  phj'siology  of,  129 
tissue,  20 
Neuman,  sheath  of,  91 
Neurons,  50 
Nevi,  415 
Nitrogen  in  urine,  determination  of,  377 

excretion  of,  390 
Nitrogenous  foods  and  muscular  activity, 
382 
physiology  of,  106 
Nodule,  definition  of,  402 
Non-nitrogenous    foods,    physiology   of, 

106 
Non-pathogenic  bacteria,  137 
Non-striated  muscles,  47 
Nutrition,  chemistry  of,  367 

physiology  of ,  106 
Nutritive  systems,  anatomy  of,  22 


Occlusion  of  teeth,  79,  221 

normal,  definition  of,  242 
Odontalgia,  266 
Odontoblasts,  91,93 
Oil  glands,  structure  of,  41 
Olfactory  groove,  59 

nerves,  54 
Optic  disk,  66 

foramen,  59 

nerve,  54 
Orbits,  anatomy  of,  62 
Organ  of  Corti,  69 
Organs,  structure  of,  18 
Osteoblasts,  98 
Osteoclasts,  99 
Otoliths,  69 
Ovarian  tissue,  20 


Palate,  anatomy  of,  74 

bones,  anatomy  of,  72 
Palatine  fossa,  anterior,  61 

posterior,  61 
Pancreas,  anatomy  of,  27 

physiology  of,  110 
Papilla)  of  tongue,  74 
Papule,  definition  of,  402 
Parasitic  affections  of  skin,  403 
animal,  405 
vegetable,  403 
Parathyroid  glands,  structure  of,  42 
Parenchymatous  inflammation,  definition 

of,  158 
Parotid  glands,  anatomy  of,  78 
Patch,  definition  of,  403 
Path  of  least  resistance,  definition  of,  165 
Pathogenic  bacteria,  138 
[  Pediculosis,  405 
capitis,  405 
corporis,  405 
pubis,  406 
,  Pepsin,  physiology  of,  109 
Peptones,  physiology  of,  112 
Pericardium,  33 

physiology  of,  118 
Pericemental  abscess,  276 
i  treatment  of,  277 

Peridental  membrane,  alveolar  portion, 
arrangement  of  fibers  in,  98 
anatomy  of,  80 
apical  portion,  arrangement  of 

fibers  in,  98 
bloodvessels  of,  99 
cells  of,  98 

changes  in,  with  age,  99 
definition  of,  95 
epithelial  elements  of,  99 
function  of,  99 
gingival   portion,    arrangement 

of  fibers  in,  96 
histology  of,  95 
nerves  of,  99 

white  fibrous  connective-tissue 
of,  95 
Perilymph,  69 
Perimysium,  50 
Periosteum,  43 
Peristalsis,  109 
Peritoneum,  25 
Phagocytosis,  117 

definition  of,  163 
Pharyngeal  tonsil,  anatomy  of,  78 
Pharynx,  anatomy  of,  24 
Physical  training  and  hygiene,  434 
Physiologj',  definition  of,  104 
Pia  mater,  structm-e  of,  53 
Pituitary  body,  structure  of,  42 
Pivot  joints,  46 
Plaque,  definition  of,  403 
Pleura,  anatomy  of,  33 
Pneumogastric  nerve,  54 
Pointing,  definition  of,  166 


528 


INDEX 


Poisoning,  ivy,  409 

sunuie,  409 
Polishing  of  teeth  in  dental  prophylaxis, 

326 
Polvmorphonuclear  leukocytes,  definition 

of,  159 
Polysaccharides,  definition  of,  370 
Pons  Varolii,  54 
Portal  circulation,  phj'siology  of,  121 

vein,  28 
Posterior  fossa  of  skull,  59 
nares,  62 
jjalatme  fossa,  61 
Postiu'e,  correct,  proper  method  of,  453 
Prickly  heat,  412 

Protein  and  muscular  activity,  382 
consumed  dailj^,  table  of,  388 
Proteins,  composition  of,  367 

phvsiologv  of,  106 
Protoplasm,  20,  104 

properties  of,  104 
Pterygoid  muscles,  218 
Ptomaines,  definition  of,  146 
Ptyalin,  109 
Pulmonary  artery,  34 

physiology  of,  120 
circulation,  physiology  of,  120 
veins,  physiology  of,  120 
Pulp  in  alveolar  abscess,  272 
anatomy  of,  80 
bloodvessels  of,  93 
cavity,  80 

connective-tissue  cells  of,  93 
function  of,  94 
histology  of,  93 
intercellular  substance  of,  93 
nerves  of,  94 
Pupil,  anatomy  of,  65 
Pus,  definition  of,  164 
Pustule,  definition  of,  402 
Putrefaction,  definition  of,  133,  144 

and  digestion,  definition  of,  145 
Pyloric  valves  of  stomach,  24 
Pylorus  of  stomach,  24 
Pyorrhea  alveolaris,  261 

and  dental  prophylaxis,  298 
etiology  of,  261 
malocclusion  and,  262 
prognosis  of,  265 
progress  of,  262 
results  of,  264 
symptoms  of,  263 
treatment  of,  263 
medical,  264 
postoperative,  264 
vaccine,  264 
Pyramids  of  Malpighi,  37 


Rectum,  anatomy  of,  27 
Red  blood  corpuscles,  159 
Reflex  nervous  action,  127 
Refractory  media  of  eyes,  66 


Renal  artery,  35 

Rennin,  physiology  of,  109 

Repair-,  definition  of,  167 

Reproductive  tissue,  20 

Reptiles,  teeth  of,  207 

Resistive  forces  of  body,  lengthening  the 

life  of,  449 
Respiration,  mechanics  of,  116,  117 

physiology  of ,  112 
Respiratory  center,  115 

system,  anatomy  of,  30 
physiology  of,  114 
Retina,  66 

Rhinoceros,  teeth  of,  217 
Ringworm,  403 

of  scalp,  404 
Rodents,  teeth  of,  213 


S 


Saccule,  69 
Saddle  joints,  46 
Sagittal  suture,  57 
Saliva,  constituents  of,  172 

decomposition  of,  175 

in  dental  caries,  196 
Salivary  glands,  anatomy  of,  27,  77 

physiology  of,  108 
Sarcolemma,  48 
Scabies,  406 
Scalp,  ringworm  of,  404 
Scarlet  fever,  417 

Sebaceous  glands,  physiology  of,  123 
Sella  turcica,  59 

Semicircular  canals,  anatomy  of,  70 
Sensory  nerve  paths,  physiology  of,  128 
Septicemia,  definition  of,  165 
Serous  exudation,  definition  of,  164 
Seventh  cranial  nerve,  anatomy  of,  77 
Sheath  of  Neuman,  91 
Sigmoid  flexure  of  colon,  27 
Sinus,  definition  of,  166 
Sinuses,  bony,  anatomy  of,  63 

frontal,  anatomy  of,  63 

maxillary,  anatomy  of,  63 

sphenoidal,  anatomy  of,  63 
Skeletal  system,  structure  of,  42 
Skeleton,  43 

appendicular,  44 

axial,  44 
Skin,  anatomy  of,  40,  401 

bloodvessels  of,  41 

diseases  of,  403 
bacterial,  407 

due  to  external  irritants,  409 
erythema  group  of,  411 

muscles  of,  41 

nerves  of,  41 

parasitic  affections  of,  403 
animal,  405 
vegetable,  403 

physiology  of,  122,  401 

pores  of,  123 
Skull,  anatomy  of,  57 


INDEX 


529 


Skull,  anterior  aspect  of,  anatomy  of,  61 

base  of,  anatomy  of,  61 

fossa?  of,  anatomy  of,  59 

lateral  aspect  of,  anatomy  of,  61 

sutures  of,  57 

vertex  of,  57 
Sliding  hinge  joints,  47 
Smooth  muscles,  48 
Snakes,  teeth  of,  207 
Soft  palate,  anatomy  of,  74 
Spec,  curve  of,  225,  226 
Spermatic  tissue,  20 
Sphenoidal  fissure,  59 

sinus,  anatomy  of,  63 
Sphenomandibular  ligament,  219 
Sphenomaxillary  fissures,  61 
Spinal  column,  bones  of,  45 

cord,  structure  of,  54 
Spirillum,  definition  of,  132 
Spirocheta  palHda,  419 
Spleen,  structure  of,  42 
Spore  formation,  133 
Steapsin,  110 
Sterilization,  definition  of,  153 

by  dry  heat,  154 

by  moist  heat,  155 
Stomach,  anatomy  of,  24 

cardiac  valves  of,  24 

fundus  of,  24 

physiology  of,  109 

pyloric  valves  of,  24 

pylorus  of,  24 
Stylomandibular  ligament,  219 
Subclavian  artery,  35 
Sublingual  glands,  anatomy  of,  78 
Submaxillary  glands,  anatomy  of,  78 
Sugar,  physiology  of,  112 
Sumac  poisoning,  409 
Superior  maxillary  bones,  anatomy  of,  70 
Supporting  tissue,  19 
Suppurative  exudation,  definition  of,  164 

inflammation,  definition  of,  158 
Sutures,  46 

coronal,  57 

lambdoid,  57 

sagittal,  57 
Sweat  glands,  anatomy  of,  41 

physiology  of,  123 
Sword-fish,  teeth  of,  217 
Sympathetic  nervous  system,  structure 

of,  56 
Syphilis,  418 

and  dental  prophylaxis,  298 

congenital,  425    • 

hereditary,  425 

history  of,  418 

methods  of  contagion  of,  419 
of  prevention  of,  419 

mucous  patch  in,  422 

stages  of,  420 
primary,  420 
secondary,  421 
tertiary,  423 
Systemic  circulation,  physiology  of,  121 

infection  and  dental  prophylaxis,  298 


Tartar,  chemistry  of,  180 
color  of,  183 
definition  of,  170 
development  of,  178 
formation  of,  178 
hardness  of,  181 
removal,  184 
solubility  of,  184 
Tartasol,  185 
Taste  buds,  74 
Teeth,  accretions  on,  170 
alveolar  process  of,  100 
anatomy  of,  78,  79,  81 
angle  of,  81 
apex  of,  81 

as  a  masticating  machine,  205 
attachment  of,  94 
of  baboon,  214 
bicuspid,  anatomy  of,  84 
bicuspids,  occlusion  of,  224 
of  black  bear,  211 
of  carnivorous  animals,  210 
cementum  of,  anatomy  of,  80 

histology  of,  91 
cervix  margin  of,  81 
of  crocodiles,  207 
cusp  of,  81 

cuspids,  anatomy  of,  82 
deciduous,  anatomy  of,  87 

eruption  of,  88 

premature  loss  of,  as  cause  of 
malocclusion,  252 
dentin  of,  anatomy  of,  80 

histology  of,  90 
deposits  on,  170 
of  dog,  212 
of  elephant,  217 
enamel  of,  anatomy  of,  80 

histology  of,  88 
of  fishes,  20'6 
of  frogs,  207 
gingival  margin  of,  81 
histology  of,  88 
of  horse,  217 
Hutchinson's,  426 
incisors,  anatomy  of,  81 
of  Indian  tiger,  211 
of  lemiu-s,  217 

lower,  occlusal  surfaces  of,  221 
malocclusion  of,  237 

classification  of,  245 
Angle's,  246 

definition  of,  244 

etiology  of,  251 

extraction    of    permanent 

teeth,    252 
lack  of  use,  253 
pernicious  habits,  252 
premature  loss  of  decidu- 
ous teeth,  252 

growth  of  jaws  in,  253 

individual,  244 
molars,  lower,  anatomy  of,  86 


530 


INDEX 


Teeth,  molars,  occlusion  of,  224; 
upper,  anatomy  of,  84 

of  monkej's,  213 

neck  of,  81 

nerve  supply  of,  70 

nomenclature  of,  81 

normal  contact  points  in,  240 

occlusion  of,  79,  221 

normal,  definition  of,  242 

peridental  membrane,  anatomy  of, 
80 
histology  of,  95 

permanent,  extraction  of,  as  cause 
of  malocclusion,  252 

pulp  of,  anatomy  of,  80 
histolog}^  of,  93 

of  reptiles,  207 

of  rhinoceros,  217 

of  rodents,  213 

of  snakes,  207 

surfaces  of,  81 

of  sword-fish,  217 

of  turtles,  207 

upper,  occlusal  surfaces  of,  221 

of  walrus,  217 
Temporal  muscles,  218 
Temporomaxillary  articulation,  anatomy 

of,  73 
Tendons,  anatomy  of,  19,  43 
Tenon,  capsule  of,  64 
Thoracic     duct,      physiology   of,      111, 

122 
Thorax,  bones  of,  45,  115 

physiology  of,  115 
Throat,  gummata  of,  426 
Thymus  gland,  structure  of,  42 
ThjToid  gland,  structure  of,  42 
Tissue,  adipose,  structure  of,  41 

areolar,  structure  of,  41 

epidermis,  40 

stimulation   in   dental   proi)hylaxis, 
341 
Tissues,  circulatory,  19 

connective,  structure  of,  43 

dental,  blood  supply  of,  75 
nerve  supply  of,  75 

epithelial,  19 

glandular,  19 

motor,  20 

nervous,  20 

ovarian,  20 

reproductive,  20 

spermatic,  20 

supporting,  19 

white  fibrous,  19 

yellow  elastic,  19 
Tomes,  granular  layer  of,  91 
Tongue,  anatomy  of,  74 

gummata  of,  426 

papilla;  of,  74 

circumvallate,  74 
Tonsil,  Ungual,  74 

anatomy  of,  78 

pharyngeal,  anatomy  of,  78 
Tonsils,  anatomy  of,  78 


Tooth-brushes  and  dental  prophylaxis, 

345 
Torsional  joints,  46 
Toxins,  definition  of,  152 
Trachea,  anatomy  of,  32 

physiology  of,  114 
Transverse  colon,  26 
Trifacial  nerve,  anatomy  of,  75 
Trypsin,  110 

Tuberculosis  and  dental  prophylaxis,  297 
Tumor,  definition  of,  402 
Turtles,  teeth  of,  207 
Tympanic  membrane,  anatomy  of,  67 


Ulcer,  definition  of,  166 

Ulcerative  inflammation,    definition   of, 

158 
Upper  extremity,  bones  of,  45 
Ureters,  anatomy  of,  38 
Urine,  nitrogen  in,  determination  of,  377 
excretion  of,  390 

physiology  of,  124 

secretion  of,  124 
Uriniferous  tubules,  37 
Urticaria,  412 
Utricle,  69 


Vaccines,  definitions  of,  147,  148 
Vagus  nerve,  54 
Valves  of  stomach,  24 
Vein,  portal,  28 
Veins,  anatomy  of,  35 

pulmonary,  physiology  of,  120 
Ventricles  of  brain,  physiology  of,  118 

structure  of,  54 
Vermiform  appendix,  26 
Vestibule  of  ear,  anatomy  of,  69 
Villi  of  intestine,  26 
Vocal  cords,  physiology  of,  114 


W 

Walrus,  teeth  of,  217 
Water,  physiology  of,  107 
White  blood  corpuscles,  159 
fibrous  tissue,  19 


X-RAYS  in  treatnuint  of  alveolar  abscess, 
281 


Yellow  elastic  tissue,  19 


Zygomatic  fossse,  61 


,-'*.*' 


m 


COLUMBIA  UNIVERSITY  LIBRARIES 

This  book  is  due  on  the  date  indicated  below,  or  at  the 
expiration  of  a  definite  period  after  the  date  of  borrowing,  as 
provided  by  the  rules  of  the  Library  or  by  special  arrange- 
ment with  the  Librarian  in  charge. 


RK53 


COLUMBIA  UNIVERSITY  LIBRARIES  (hsi.stx) 

RK53.F731916C.1 

Mouth  hvQiene 


2002356651 


